Salt and photoresist composition containing the same

ABSTRACT

A salt represented by formula (I): 
     
       
         
         
             
             
         
       
     
     wherein Q 1  and Q 2  independently each represent a fluorine atom or a C1-C6 perfluoroalkyl group,
 
R 1  and R 2  independently each represent a hydrogen atom, a fluorine atom or a C1-C6 perfluoroalkyl group,
 
z represents an integer of 0 to 6,
 
X 1  represents *—C(═O)—O—, *—O—C(═O)—, *—O—C(═O)—O— or —O—, where * represents a binding site to —C(R 1 )(R 2 )— or —C(Q 1 )(Q 2 )-,
 
A 1  represents a C2-C36 divalent hydrocarbon group in which a methylene group can be replaced by an oxygen atom, a sulfur atom, a carbonyl group or a sulfonyl group and in which a hydrogen atom can be replaced by a substituent,
 
R 3  represents a hydrogen atom or a methyl group, and
 
Z +  represents an organic cation.

This nonprovisional application claims priority under 35 U.S.C. § 119(a)on No. 2016-171968 filed in JAPAN on Sep. 2, 2016, the entire contentsof which are hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to a salt and a photoresist compositioncontaining the same.

BACKGROUND OF THE INVENTION

US2007/0149702A1 mentions an acid generator which contains a salt.

US2007/0100096A1 mentions a photoresist composition comprising thefollowing salt as an acid generator.

JP2013-82893A1 mentions a photoresist composition which comprises a saltas an acid generator.

SUMMARY OF THE INVENTION

The present invention relates to the followings:

<1> A salt represented by formula (I):

wherein Q¹ and Q² independently each represent a fluorine atom or aC1-C6 perfluoroalkyl group,

R¹ and R² independently each represent a hydrogen atom, a fluorine atomor a C1-C6 perfluoroalkyl group,

z represents an integer of 0 to 6,

X¹ represents *—C(═O)—O—, *—O—C(═O)—, *—O—C(═O)—O— or —O—, where *represents a binding site to —C(R¹)(R²)— or —C(Q¹)(Q²)-,

A¹ represents a C2-C36 divalent hydrocarbon group in which a methylenegroup can be replaced by an oxygen atom, a sulfur atom, a carbonyl groupor a sulfonyl group and in which a hydrogen atom can be replaced by asubstituent,

R³ represents a hydrogen atom or a methyl group, and

Z⁺ represents an organic cation.

<2> The salt according to <1> wherein X¹ represents *—C(═O)—O—.

<3> The salt according to <1> or <2> wherein the divalent hydrocarbongroup represented by A¹ has a C3-C18 alicyclic hydrocarbon group.

<4> The salt according to any one of <1> to <3> wherein R³ is a hydrogenatom.

<5> An acid generator comprising the salt according to any one of <1> to<4>.

<6> A photoresist composition comprising the salt according to any oneof <1> to <5> as an acid generator and a resin which comprises astructural unit having an acid-labile group.

<7> The photoresist composition according to <6> which further comprisesa salt generating an acid weaker in acidity than an acid generated fromthe acid generator.

<8> A process for producing a photoresist pattern comprising thefollowing steps (1) to (5):

(1) a step of applying the photoresist composition according to <6> on asubstrate,

(2) a step of forming a composition film by conducting drying,

(3) a step of exposing a composition film to radiation,

(4) a step of baking the exposed composition film, and

(5) a step of developing the baked composition film with an alkalinedeveloper, thereby forming a photoresist pattern.

DESCRIPTION OF EMBODIMENTS

The salt of the disclosure is represented by the formula (I):

in which Q¹ and Q² independently each represent a fluorine atom or aC1-C6 perfluoroalkyl group,

R¹ and R² independently each represent a hydrogen atom, a fluorine atomor a C1-C6 perfluoroalkyl group,

z represents an integer of 0 to 6,

X¹ represents *—C(═O)—O—, *—O—C(═O)—, *—O—C(═O)—O— or —O—, where *represents a binding site to —C(R¹)(R²)— or —C(Q¹)(Q²),

A¹ represents a C2-C36 divalent hydrocarbon group in which a methylenegroup can be replaced by an oxygen atom, a sulfur atom, a carbonyl groupor a sulfonyl group and in which a hydrogen atom can be replaced by asubstituent,

R³ represents a hydrogen atom or a methyl group, and

Z⁺ represents an organic cation.

For Q¹, Q², R¹ and R², examples of the perfluoroalkyl group include atrifluoromethyl group, a pentafluoroethyl group, a heptafluoropropylgroup, a nonafluorobutyl group, an undecafluoropentyl group and atridecafluorohexyl group, and a trifluoromethyl group is preferred.

Q¹ and Q² each independently preferably represent a fluorine atom or atrifluoromethyl group, and Q and Q² are more preferably fluorine atoms.

R¹ and R² each independently preferably represent a hydrogen atom or afluorine atom. z is preferably 0.

X¹ preferably represents *—C(═O)—O— where * represents a binding site to—C(R¹)(R²)— or —C(Q¹)(Q²)-.

As to A¹, examples of the C2-C36 divalent hydrocarbon group include aC2-C36 alkylene group, a C3-C36 divalent monocyclic or polycyclicalicyclic hydrocarbon group, a C6-C36 aromatic hydrocarbon group and anycombination of them.

Examples of the saturated hydrocarbon group include linear alkylenegroups such as an ethylene group, a propane-1,3-diyl group, abutane-1,4-diyl group, a pentane-1,5-diyl group, a hexane-1,6-diylgroup, a heptane-1,7-diyl group, an octane-1,8-diyl group, anonane-1,9-diyl group, a decane-1,10-diyl group, an undecane-1,1-diylgroup and a dodecane-1,12-diyl group;

branched alkylene groups such as an ethane-1,1-diyl group, apropane-1,1-diyl group, a propane-1,2-diyl group, a propane-2,2-diylgroup, a pentane-2,4-diyl group, a 2-methylpropane-1,3-diyl group,2-methylpropane-1,2-diyl group, pentane-1,4-diyl group, and2-methylbutane-1,4-diyl group;

divalent monocyclic alicyclic hydrocarbon groups such ascyclobutane-1,3-diyl group, cyclopentane-1,3-diyl group,cyclohexane-1,4-diyl group and cyclooctane-1,5-diyl group;

divalent polycyclic alicyclic hydrocarbon groups such asnorbornane-1,4-diyl group, norbornane-2,5-diyl group,adamantane-1,5-diyl group and adamantane-2,6-diyl group; and

divalent aromatic hydrocarbon group such as a phenylene group, anaphthylene group, an anthrylene group, a p-methylphenylene group, ap-tert-butylphenylene group, a p-adamantylphenylene group, a tolylenegroup, a xylylene group, a cumylene group, a mesitylene group, abiphenylene group, a phenanthrylene group, a 2, 6-diethylphenylene groupand a 2-methyl-6-ethylphenylene group. The divalent hydrocarbon grouprepresented by A¹ can have a substituent. Examples of the substituentinclude a hydroxyl group, a cyano group, a carboxyl group, a C1-C12alkoxy group, a C2-C13 alkoxycarbonyl group, a C2-C13 alkoxycarbonyloxygroup, or any combination of these groups.

Examples of the alkoxy group include a methoxy group, an ethoxy group, apropoxy group, a butoxy group, a pentyloxy group and a hexyloxy group.

Examples of the alkylcarbony group include an acetyl group, a propyonylgroup and a butyryl group.

Examples of alkylcarbonyloxy group include a methylcarbonyloxy group, anethylcarbonyloxy group, a propylcarbonyloxy group and a butylcarbonyloxygroup.

In the divalent hydrocarbon group represented by A¹, a methylene groupcan be replaced by an oxygen atom, a sulfur atom, a carbonyl group or asulfonyl group.

The divalent hydrocarbon group represented by A¹ has preferably a C3-C18alicyclic hydrocarbon group, more preferably a cyclohexanediyl group oran adamantanediyl group. A¹ is preferably a divalent hydrocarbon groupcomposed of a C1-C6 alkyl group and a cyclohexanediyl or adamantanediylgroup.

R³ is preferably a hydrogen atom.

Specific examples of the anion for the salt represented by formula (I)include the following ones. Among them, an anion represented by any oneof formulae (Ia-1) to (Ia-11), (Ia-13) to (Ia-20) and (Ia-22) ispreferred, and an anion represented by any one of formulae (Ia-1) to(Ia-3) and (Ia-13) to (Ia-16) is more preferred.

Examples of the organic cation represented by Z⁺ include an organiconium cation such as an organic sulfonium cation, an organic iodoniumcation, an organic ammonium cation, a benzothiazolium cation and anorganic phosphonium cation. As Z⁺, an organic sulfonium cation and anorganic iodonium cation are preferred, and an arylsulfonium cation ismore preferred. Herein, the arylsulfonium includes those having one, twoor three aryl groups.

Preferable examples of the organic cation represented by Z⁺ include theorganic cations represented by the formulae (b2-1) to b4):

wherein R^(b4), R^(b5) and R^(b6) independently represent a C1-C30aliphatic hydrocarbon group in which a hydrogen atom can be replaced bya hydroxy group, a C1-C12 alkoxy group or a C6-C18 alicyclic hydrocarbongroup,

a C3-C36 alicyclic hydrocarbon group in which a hydrogen atom can bereplaced by a halogen atom, a C2-C4 acyl group or a glycidyloxy group,and

a C6-C36 aromatic hydrocarbon group in which a hydrogen atom can bereplaced by a halogen atom, a hydroxy group, or C1-C12 alkoxy group; andR^(b4) and R^(b5), R^(b4) and R^(b6), or R^(b5) and R^(b6) can be bondedeach other to form a ring containing S⁺;

R^(b7) and R^(b8) are independently in each occurrence a hydroxy group,a C1-C12 alkyl group or a C1-C12 alkoxy group;

m2 and n2 independently represents an integer of 0 to 5;

R^(b9) and R^(b10) independently represent a C1-C36 aliphatichydrocarbon group or a C3-C36 alicyclic hydrocarbon group, or R^(b9) andR^(b10) are bonded each other to form a ring together with the adjacent—S⁺—, and one or more —CH₂— in the ring may be replaced by an oxygenatom, a sulfur atom or carbonyl group; and

R^(b11) represents a hydrogen atom, a C1-C36 aliphatic hydrocarbongroup, a C3-C36 alicyclic hydrocarbon group, or a C6-C18 aromatichydrocarbon group, and R^(b12) represents a C1-C12 aliphatic hydrocarbongroup where a hydrogen atom can be replaced by a C6-C18 aromatichydrocarbon group, a C3-C18 alicyclic hydrocarbon group, and a C6-C18aromatic hydrocarbon group optionally substituted with a C1-C12 alkoxygroup or a C1-C12 alkylcarbonyloxy group; or R^(b11) and R^(b12) arebonded each other to form a C1-C10 divalent alicyclic hydrocarbon groupwhich forms a 2-oxocycloalkyl group together with the adjacent —CHCO—,and one or more —CH₂— in the group may be replaced by an oxygen atom, asulfur atom or carbonyl group; and

R^(b13), R^(b14), R^(b15), R^(b16), R^(b17) and R^(b18) independentlyrepresent a hydroxy group, a C1-C12 alkyl group or a C1-C12 alkoxygroup;

L^(b31) represents —S— or —O—; and

o2, p2, s2 and t2 each independently represents an integer of 0 to 5;

q2 and r2 each independently represents an integer of 0 to 4; and

u2 represents 0 or 1.

Examples of the aliphatic hydrocarbon group represented by eachsubstituent include an alkyl group such as a methyl group, an ethylgroup, a propyl group, an isopropyl group, a butyl group, a sec-butylgroup, a tert-butyl group, a pentyl group, a hexyl group, an octylgroup, and a 2-ethylhexyl group. The aliphatic hydrocarbon grouprepresented by R^(b9) to R^(b12) is preferably a C1-C18 alkyl group,more preferably a C1-C12 alkyl group.

Examples of the alkyl group where a hydrogen atom has been replaced byan alicyclic hydrocarbon group include 1-(adamantane-1-yl) alkane-1-ylgroup.

The alicyclic hydrocarbon group represented by each substituent may bemonocyclic or polycyclic, a hydrogen atom of which can be replaced by analkyl group. When a hydrogen atom of it has been replaced by an alkylgroup, the total number of carbon atoms is 30 or less.

Examples of the monocyclic alicyclic hydrocarbon group include acycloalkyl group such as a cyclopropyl group, a cyclobutyl group, acyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclodecylgroup.

Examples of the polycyclic alicyclic hydrocarbon group include adecahydronaphtyl group, an adamantyl group, a norbornyl group, and thefollowing ones.

The alicyclic hydrocarbon group represented by R^(b9) to R^(b12) haspreferably 3 to 18, more preferably 4 to 12, carbon atoms.

Examples of the alicyclic hydrocarbon group where a hydrogen atom hasbeen replaced by an alkyl group include a methylcyclohexyl group, a2-alkyladamantane-2-yl group, a methylnorbornyl group, and an isobornylgroup.

Preferable examples of the aromatic hydrocarbon group includesubstituted or unsubstituted phenyl group such as a phenyl group, atolyl group, a xylyl group, a cumenyl group, a mesityl group, a4-ethylphenyl group, 4-tert-butylphenyl group, 4-cyclohexylphenyl group,a 4-adamantylphenyl group, a 2, 6-diethylphenyl group, a2-methyl-6-ethylphenyl group; a biphenyl group, a naphtyl group, aphenanthryl group.

Preferable examples of the aromatic hydrocarbon group where a hydrogenatom has been replaced by an alkoxy group include 4-methoxyphenyl group.

Preferable examples of the alkyl group where a hydrogen atom has beenreplaced by an aromatic hydrocarbon group, i.e., an aralkyl group,include a benzyl group, a phenethyl group, a phenylpropyl group, atrityl group, a naphthylmethyl group and a naphthylethyl group.

When the aromatic hydrocarbon group has an alkyl group or an alicyclichydrocarbon group as a substituent, the substituent is preferably aC1-C12 alkyl group or a C3-C18 alicyclic hydrocarbon group.

Examples of the alkoxy group include a methoxy group, an ethoxy group, apropoxy group, a butoxy group, a pentyloxy group, a hexyloxy group, aheptyloxy group, an octyloxy group, a decyloxy group and a dodecyloxygroup.

Examples of the C2-C4 acyl group include an acetyl group, a propionylgroup and a butyryl group.

Examples of the halogen atom include a fluorine atom, a chlorine atom, abromine atom and an iodine atom.

Preferable examples of the alkylcarbonyloxy group include amethylcarbonyloxy group, an ethylcarbonyloxy group, n-propylcarbonyloxygroup, an isopropylcarbonyloxy group, n-butylcarbonyloxy group,sec-butylcarbonyloxy group, a tert-butylcarbonyloxy group, apentylcarbonyloxy group, a hexylcarbonyloxy group, an octylcarbonyloxygroup and 2-ethyl hexylcarbonyloxy group.

The ring containing S⁺ formed by bonding R^(b4) and R^(b5), R^(b4) andR^(b6), or R^(b5) and R^(b6) each other may be a monocyclic ring, apolycyclic ring, an aromatic ring, a non-aromatic ring, a saturated ringor a unsaturated ring. The ring can contain a sulfur atom or oxygen atomin addition to S⁺. The ring preferably has 3 to 18 carbon atoms, andmore preferably has 4 to 13 carbon atoms. Examples of such ring include,3 to 12-membered rings, preferably 3 to 7-membered rings, specificallythe following ones.

Examples of the ring group formed by bonding R^(b9) and R^(b10) togetherwith the adjacent S⁺ and the divalent alicyclic hydrocarbon groupinclude, 3 to 12-membered rings, preferably 3 to 7-membered rings,specifically a thiolan-1-ium ring (tetrahydrothiophenium ring), athian-1-ium ring and a 1,4-oxathian-4-ium ring.

Examples of the ring group formed by bonding R^(b11) and R^(b12) include3 to 12-membered rings, preferably 3 to 7-membered rings, specificallyoxocyclopentane ring, oxocyclohexane ring, oxonorbornane ring andoxoadamantane ring.

Among the above-mentioned cations, preferred is the cation representedby the formula (b2-1).

Examples of the cation represented by the formula (b2-1) include thefollowing ones.

Examples of the cation represented by the formula (b2-2) include thefollowing ones.

Examples of the cation represented by the formula (b2-3) include thefollowing ones.

Examples of the cation represented by the formula (b2-4) include thefollowing ones.

Among them, a cation represented by any one of formulae (b2-c-1),(b2-c-10), (b2-c-12), (b2-c-14), (b2-c-27), (b2-c-30) and (b2-c-31) ispreferred.

Specific examples of the salt represented by formula (I) are listed inthe following tables.

In those tables, every character in each column represents a sign whichrepresents one of the chemical formulae specifically illustrated above.For example, the salt (I-1) consists of the anion of formula (Ia-1) andthe cation of formula (b2-c-1) as shown below.

TABLE 1 Salt anion cation (I-1) (Ia-1) (b2-c-1) (I-2) (Ia-2) (b2-c-1)(I-3) (Ia-3) (b2-c-1) (I-4) (Ia-4) (b2-c-1) (I-5) (Ia-5) (b2-c-1) (I-6)(Ia-6) (b2-c-1) (I-7) (Ia-7) (b2-c-1) (I-8) (Ia-8) (b2-c-1) (I-9) (Ia-9)(b2-c-1) (I-10) (la-10) (b2-c-1) (I-11) (Ia-11) (b2-c-1) (I-12) (Ia-12)(b2-c-1) (I-13) (Ia-13) (b2-c-1) (I-14) (Ia-14) (b2-c-1) (I-15) (Ia-15)(b2-c-1) (I-16) (Ia-16) (b2-c-1) (I-17) (Ia-17) (b2-c-1) (I-18) (Ia-18)(b2-c-1) (I-19) (Ia-19) (b2-c-1) (I-20) (Ia-20) (b2-c-1) (I-21) (Ia-21)(b2-c-1) (I-22) (Ia-22) (b2-c-1) (I-23) (Ia-1) (b2-c-10) (I-24) (Ia-2)(b2-c-10) (I-25) (Ia-3) (b2-c-10) (I-26) (Ia-4) (b2-c-10) (I-27) (Ia-5)(b2-c-10) (I-28) (Ia-6) (b2-c-10) (I-29) (Ia-7) (b2-c-10) (I-30) (Ia-8)(b2-c-10) (I-31) (Ia-9) (b2-c-10) (I-32) (Ia-10) (b2-c-10) (I-33)(Ia-11) (b2-c-10) (I-34) (Ia-12) (b2-c-10) (I-35) (Ia-13) (b2-c-10)(I-36) (Ia-14) (b2-c-10) (I-37) (Ia-15) (b2-c-10) (I-38) (Ia-16)(b2-c-10) (I-39) (Ia-17) (b2-c-10) (I-40) (Ia-18) (b2-c-10)

TABLE 2 Salt anion cation (I-41) (Ia-19) (b2-c-10) (I-42) (Ia-20)(b2-c-10) (I-43) (Ia-21) (b2-c-10) (I-44) (Ia-22) (b2-c-10) (I-45)(Ia-1) (b2-c-12) (I-46) (Ia-2) (b2-c-12) (I-47) (Ia-3) (b2-c-12) (I-48)(Ia-4) (b2-c-12) (I-49) (Ia-5) (b2-c-12) (I-50) (Ia-6) (b2-c-12) (I-51)(Ia-7) (b2-c-12) (I-52) (Ia-8) (b2-c-12) (I-53) (Ia-9) (b2-c-12) (I-54)(la-10) (b2-c-12) (I-55) (Ia-11) (b2-c-12) (I-56) (Ia-12) (b2-c-12)(I-57) (Ia-13) (b2-c-12) (I-58) (Ia-14) (b2-c-12) (I-59) (Ia-15)(b2-c-12) (I-60) (Ia-16) (b2-c-12) (I-61) (Ia-17) (b2-c-12) (I-62)(Ia-18) (b2-c-12) (I-63) (Ia-19) (b2-c-12) (I-64) (Ia-20) (b2-c-12)(I-65) (Ia-21) (b2-c-12) (I-66) (Ia-22) (b2-c-12) (I-67) (Ia-1)(b2-c-14) (I-68) (Ia-2) (b2-c-14) (I-69) (Ia-3) (b2-c-14) (I-70) (Ia-4)(b2-c-14) (I-71) (Ia-5) (b2-c-14) (I-72) (Ia-6) (b2-c-14) (I-73) (Ia-7)(b2-c-14) (I-74) (Ia-8) (b2-c-14) (I-75) (Ia-9) (b2-c-14) (I-76) (Ia-10)(b2-c-14) (I-77) (Ia-11) (b2-c-14) (I-78) (Ia-12) (b2-c-14) (I-79)(Ia-13) (b2-c-14) (I-80) (Ia-14) (b2-c-14)

TABLE 3 Salt anion Cation (I-81) (Ia-15) (b2-c-14) (I-82) (Ia-16)(b2-c-14) (I-83) (Ia-17) (b2-c-14) (I-84) (Ia-18) (b2-c-14) (I-85)(Ia-19) (b2-c-14) (I-86) (Ia-20) (b2-c-14) (I-87) (Ia-21) (b2-c-14)(I-88) (Ia-22) (b2-c-14) (I-89) (Ia-1) (b2-c-27) (I-90) (Ia-2) (b2-c-27)(I-91) (Ia-3) (b2-c-27) (I-92) (Ia-4) (b2-c-27) (I-93) (Ia-5) (b2-c-27)(I-94) (Ia-6) (b2-c-27) (I-95) (Ia-7) (b2-c-27) (I-96) (Ia-8) (b2-c-27)(I-97) (Ia-9) (b2-c-27) (I-98) (la-10) (b2-c-27) (I-99) (Ia-11)(b2-c-27) (I-100) (Ia-12) (b2-c-27) (I-101) (Ia-13) (b2-c-27) (I-102)(Ia-14) (b2-c-27) (I-103) (Ia-15) (b2-c-27) (I-104) (Ia-16) (b2-c-27)(I-105) (Ia-17) (b2-c-27) (I-106) (Ia-18) (b2-c-27) (I-107) (Ia-19)(b2-c-27) (I-108) (Ia-20) (b2-c-27) (I-109) (Ia-21) (b2-c-27) (I-110)(Ia-22) (b2-c-27) (I-111) (Ia-1) (b2-c-30) (I-112) (Ia-2) (b2-c-30)(I-113) (Ia-3) (b2-c-30) (I-114) (Ia-4) (b2-c-30) (I-115) (Ia-5)(b2-c-30) (I-116) (Ia-6) (b2-c-30) (I-117) (Ia-7) (b2-c-30) (I-118)(Ia-8) (b2-c-30) (I-119) (Ia-9) (b2-c-30) (I-120) (Ia-10) (b2-c-30)

TABLE 4 Salt anion Cation (I-121) (Ia-11) (b2-c-30) (I-122) (Ia-12)(b2-c-30) (I-123) (Ia-13) (b2-c-30) (I-124) (Ia-14) (b2-c-30) (I-125)(Ia-15) (b2-c-30) (I-126) (Ia-16) (b2-c-30) (I-127) (Ia-17) (b2-c-30)(I-128) (Ia-18) (b2-c-30) (I-129) (Ia-19) (b2-c-30) (I-130) (Ia-20)(b2-c-30) (I-131) (Ia-21) (b2-c-30) (I-132) (Ia-22) (b2-c-30) (I-133)(Ia-1) (b2-c-31) (I-134) (Ia-2) (b2-c-31) (I-135) (Ia-3) (b2-c-31)(I-136) (Ia-4) (b2-c-31) (I-137) (Ia-5) (b2-c-31) (I-138) (Ia-6)(b2-c-31) (I-139) (Ia-7) (b2-c-31) (I-140) (Ia-8) (b2-c-31) (I-141)(Ia-9) (b2-c-31) (I-142) (la-10) (b2-c-31) (I-143) (Ia-11) (b2-c-31)(I-144) (Ia-12) (b2-c-31) (I-145) (Ia-13) (b2-c-31) (I-146) (Ia-14)(b2-c-31) (I-147) (Ia-15) (b2-c-31) (I-148) (Ia-16) (b2-c-31) (I-149)(Ia-17) (b2-c-31) (I-150) (Ia-18) (b2-c-31) (I-151) (Ia-19) (b2-c-31)(I-152) (Ia-20) (b2-c-31) (I-153) (Ia-21) (b2-c-31) (I-154) (Ia-22)(b2-c-31)

Among these specific examples, the salt represented by formula (I) ispreferably salt(I-1), salt(I-2), salt(I-3), salt(I-15), salt(I-16),salt(I-23), salt(I-24), salt(I-37), salt(I-38), salt(I-45), salt(I-46),salt(I-59), salt(I-60), salt(I-67), salt(I-68), salt(I-81), salt(I-82),salt(I-89), salt(I-90), salt(I-103), salt(I-104), salt(I-111),salt(I-112), salt(I-125), salt(I-126), salt(I-133), salt(I-134),salt(I-147), salt(I-148).

The process for producing the salt represented by formula (I) will beillustrated.

When the salt represented by formula (I) has *—C(═O)—O— as X¹, it can beproduced by reacting a salt represented by the formula (I1-a) with thecompound represented by formula (I1-b) in a solvent such as chloroformor acetonitrile:

wherein Q¹, Q², R¹, R², R³, z, A¹ and Z⁺ are the same as defined above,and the formula (I1) represents the salt represented by formula (I) inwhich X¹ is *—C(═O)—O—.

The above-mentioned reaction is usually conducted at about 5 to 80° C.,for 0.5 to 24 hours.

Specific examples of the salt represented by the formula (I1-a) includethe following ones, which are available in the market.

Specific examples of the compound represented by the formula (I1-b)include the following ones. These compounds are available in the market.

When the salt represented by formula (I) has *—O—C(═O)—O— as X¹, it canbe produced by reacting a salt represented by the formula (I2-a) withthe compound represented by formula (I1-b) in a solvent such aschloroform or acetonitrile:

wherein Q¹, Q², R¹, R², R³, z, A¹ and Z⁺ are the same as defined above,and formula (I2) represents the salt represented by formula (I) in whichX¹ is *—O—C(═O)—O—

The above-mentioned reaction is usually conducted at about 5 to 80° C.,for 0.5 to 24 hours.

The salt represented by formula (I2-a) can be produced by reacting asalt represented by the formula (I2-c) with the compound represented byformula (I2-d) in a solvent such as chloroform or acetonitrile:

wherein Q¹, Q², R¹, R², z and Z⁺ are the same as defined above.

The above-mentioned reaction is usually conducted at about 5 to 80° C.,for 0.5 to 24 hours.

Specific examples of the salt represented by the formula (I1-c) includethe following ones, which can be produced according to the methodrecited in JP2012-193170A1.

When the salt represented by formula (I) has *—O—C(═O)— as X¹, it can beproduced by reacting a salt represented by the formula (I2-c) with thecompound represented by formula (I3-b), in the presence of a base suchas potassium carbonate, potassium iodide, pyridine,dimethylaminopyridine, in a solvent such as chloroform or acetonitrile:

wherein Q¹, Q², R¹, R², R³, z, A¹ and Z⁺ are the same as defined above,and the salt represented by formula (I) in which X¹ is *—O—C(═O)— isrepresented by formula (I3).

The above-mentioned reaction is usually conducted at about 5 to 80° C.,for 0.5 to 24 hours.

Specific examples of the salt represented by the formula (I3-b) includethe following ones, which are available on the market.

When the salt represented by formula (I) has —O— as X¹, it can beproduced by reacting a salt represented by the formula (I2-c) with thecompound represented by formula (I1-b), in the presence of a base suchas potassium carbonate, in a solvent such as chloroform or acetonitrile:

<Acid Generator>

The acid generator of the disclosure comprises the salt represented byformula (I). The acid generator may contain two or more of the saltrepresented by formula (I). The acid generator may contain a known acidgenerator, which is described later, in addition to the salt representedby formula (I).

In the photoresist composition, an acid generates from the acidgenerator by light for lithography. The acid catalytically acts againstan acid-labile group in the resin to cleave the acid-labile group.

When the acid generator contains a known acid generator, the weightratio of the salt and the known acid generator is usually 1:99 to 99:1,preferably 2:98 to 98:2, more preferably 5:95 to 95:5, still morepreferably 10:90 to 90:10.

<Photoresist Composition>

The photoresist composition of the disclosure comprises the saltrepresented by formula (I) as an acid generator and a resin having anacid-labile group which resin is referred to as “Resin (A)”. Thephotoresist composition may further contain a known acid generator, aquencher, or solvent. Hereinafter, a known acid generator is referred toas “acid generator (B)”.

The content of the salt represented by formula (I) is preferably 0.1 to35% by mass, more preferably 0.5 to 30% by mass, still more preferably 1to 25% by mass of solid components.

Resin (A) usually has a structural unit having an acid-labile group.Hereinafter, the structural unit is sometimes referred to as “structuralunit (a1)”.

Preferably Resin (A) further has another structural unit than thestructural unit (a1), i.e. a structural unit having no acid-labilegroup, which is sometimes referred to as “structural unit (s)”.

Herein, “an acid-labile group” means a group which has a hydrophilicgroup, such as a hydroxy group or a carboxy group, resulting fromremoving a leaving group therefrom by the action of an acid.

The structural unit (a1) is derived from a monomer having an acid-labilegroup which is sometimes referred to as “monomer (a1)”. Specificexamples of the acid-labile group include a group represented by theformula (1):

wherein R^(a1), R^(a2) and R^(a3) each independently represent a C1-C8alkyl group, a C3-C20 alicyclic hydrocarbon group or a combination ofthem, or R^(a1) and R^(a2) may be bonded each other to form a C3-C20divalent alicyclic hydrocarbon group together with the carbon atombonded to both of them, “na” represents an integer of 0 or 1, and *represents a binding site,

and a group represented by the formula (2):

wherein R^(a1′) and R^(a2′) each independently represent a hydrogen atomor a C1-C12 hydrocarbon group, and R^(a3′) represents a C1-C20hydrocarbon group, or R^(a3′) is bonded to R^(a1′) or R^(a2′) to form aC2-C20 divalent heterocyclic group with a carbon atom and X bondedthereto, a methylene group in the divalent heterocyclic group may bereplaced by —O— or —S—, X represents an oxygen atom or a sulfur atom,and * represents a binding site.

Specific examples of the C1-C8 alkyl group include a methyl group, anethyl group, a propyl group, an isopropyl group, a butyl group, a pentylgroup, a hexyl group, a heptyl group and an octyl group.

The alicyclic hydrocarbon group may be monocyclic or polycyclic.

Examples of the alicyclic hydrocarbon group include a monocyclicalicyclic hydrocarbon group such as a C3-C20 cycloalkyl group (e.g. acyclopentyl group, a cyclohexyl group, a methylcyclohexyl group, adimethylcyclohexyl group, a cycloheptyl group and a cyclooctyl group)and a polycyclic alicyclic hydrocarbon group such as a decahydronaphthylgroup, an adamantyl group, a norbornyl group, and the followings.

The alicyclic hydrocarbon group preferably has C3-C16 carbon atoms. Thecombination of alkyl group and alicyclic hydrocarbon group includes amethylcyclohexyl group, a dimethylcyclohexyl group, a methylnorbornylgroup, a cyclohexylmethyl group, an adamantylmethyl group, anorbornylethyl group.

When R^(a1) and R^(a2) of formula (1) are bonded each other to form aC2-C20 divalent hydrocarbon group, examples of the moiety represented by—C(R^(a1))(R^(a2))(R^(a3)) include the following groups and the ringpreferably has 3 to 12 carbon atoms:

wherein R^(a) is as defined above and * represents a binding site.

Specific examples of the groups represented by formula (1) include thefollowing ones:

in which * represents a binding site.

As the group represented by the formula (1), preferred are1,1′-dialkylalkoxylcarbonyl group, i.e., the group represented by theformula (1) wherein R^(a1), R^(a2) and R^(a3) each independentlyrepresent a C1-C8 alkyl group, preferably a tert-butyl group;

2-alkyladaman-2-tyloxycarbonyl group, i.e., the group represented by theformula (1) wherein R^(a1) and R^(a2) are bonded each other to form anadamantyl group and R^(a3) is a C1-C8 alkyl group; and a1-(1-adaman-1-tyl)-1-alkylalkoxycarbonyl group, i.e., the grouprepresented by the formula (1) wherein R^(a1) and R^(a2) are C1-C8 alkylgroups and R^(a3) is an adamantyl group.

As to formula (2), examples of the hydrocarbon group include an alkylgroup, an alicyclic hydrocarbon group, an aromatic hydrocarbon group,and any combination of these hydrocarbon groups. Examples of the alkylgroup and the alicyclic hydrocarbon group include the same as describedabove.

Examples of the aromatic hydrocarbon group include an aryl group such asa phenyl group, a naphthyl group, an anthryl group, a p-methylphenylgroup, a p-tert-butylphenyl group, a p-adamantylphenyl group, a tolylgroup, a xylyl group, a cumyl group, a mesityl group, a biphenyl group,a phenanthryl group, a 2,6-diethylphenyl group and a2-methyl-6-ethylphenyl group.

Examples of the divalent heterocyclic group formed by bonding withR^(a2′) or R^(a3′) with a carbon atom and X bonded thereto include thefollowing groups.

In each formula, R^(a1′), X and * are as defined above.

Preferably, at least one of R^(a1′) and R^(a2′) is a hydrogen atom.Examples of the group represented by formula (2) include the following.

The monomer (a1) is preferably a compound having an acid-labile groupand a carbon-carbon double bond, and is more preferably a (meth)acrylatecompound having an acid-labile group.

Such (meth)acrylate compound preferably has a C5-C20 alicyclichydrocarbon group. When the photoresist composition has a resin whichhas a structural unit with a bulky structure such as a saturatedalicyclic hydrocarbon group, the photoresist composition can provide aphotoresist pattern with excellent resolution.

Specific examples of the structural unit derived from the (meth)acrylatecompound having a group of formula (1) include those represented by theformulae (a1-0), (a1-1) and (a1-2). The structural units represented bythe formulae (a1-0), (a1-1) and (a1-2) are sometimes referred to as“structural unit (a1-0)”, “structural unit (a1-1)” and “structural unit(a1-2)”, respectively. The monomers from which the structural unit(a1-0), (a1-1) and (a1-2) are derived are sometimes referred to as“monomer (a1-0)”, “monomer (a1-1)” and “monomer (a1-2)”, respectively.

In formulae (a1-0), (a1-1) and (a1-2), L^(a01) each independentlyrepresents an oxygen atom or *—O—(CH₂)_(k01)—CO—O— in which * representsa binding site to —CO—, and k01 represents an integer of 1 to 7;

R^(a01) each independently represent a hydrogen atom or a methyl group;

R^(a02), R^(a03) and R^(a04) each independently represent a C1-C8 alkylgroup, a C3-C18 alicyclic hydrocarbon group, or a combination of them;

L^(a1) and L^(a2) each independently represents an oxygen atom or*—O—(CH₂)_(k1)—CO—O— in which * represents a binding site to —CO—, andk1 represents an integer of 1 to 7;

R^(a4) and R^(a5) each independently represent a hydrogen atom or amethyl group;

R^(a6) and R^(a7) each independently represent a C1-C8 alkyl group, aC3-C18 alicyclic hydrocarbon group, or a combination of them;

“m1” represents an integer of 0 to 14; “n1” represents an integer of 0to 10; and “n1′” represents 0 to 3.

L^(a01) is preferably an oxygen atom or *—O—(CH₂)_(f01)—CO—O— in which *represents a binding site to —CO—, and “f01” represents an integer of 1to 4, and is more preferably an oxygen atom.

“f01” represents preferably an integer of 1 to 4, more preferably 1.

Examples of the alkyl group, the alicyclic hydrocarbon group and thecombination of them, represented by R^(a02), R^(a03) and R^(a04),include those same as examples of the alkyl group, the alicyclichydrocarbon group and the combination of them for R^(a1), R^(a2) andR^(a3)

The alkyl group represented by R^(a02), R^(a03) or R^(a04) is preferablya C1-C6 alkyl group.

The alicyclic hydrocarbon group represented by R^(a02), R^(a03) orR^(a04) has preferably 8 or less, and more preferably 6 or less ofcarbon atoms.

The combination of the alkyl group and the alicyclic hydrocarbon group,as a group represented by R^(a02), R^(a03) or R^(a04), has preferably 18or less of carbon atoms. Examples of the combination include amethylcyclohexyl group, dimethylcyclohexyl group, a methylnorbornylgroup, a methyladamantyl group, a (cyclohexyl)methyl group, a methylcyclohexylmethyl group, an adamantylmethyl group, and a norbornylmethylgroup.

R^(a02) and R^(a03) are each preferably a C1-C6 alkyl group, morepreferably a methyl group or an ethyl group.

R^(a04) is preferably a C1-C6 alkyl group or a C5-C12 alicyclichydrocarbon group, more preferably a methyl group, an ethyl group, acyclohexyl group or an adamantyl group.

L^(a1) and L^(a2) are preferably an oxygen atom or *—O—(CH₂)_(f1)—CO—O—in which * represents a binding site to —CO—, and “f1” represents aninteger of 1 to 4, and is more preferably an oxygen atom.

“f1” represents preferably an integer of 1 to 4, more preferably aninteger of 1.

R^(a4) and R^(a5) are each preferably a methyl group.

Examples of the alkyl group, the alicyclic hydrocarbon group and thecombination of them, represented by R^(a6) and R^(a7), include thosesame as examples for R^(a1), R^(a2) and R^(a3).

The alkyl group represented by R^(a6) or R^(a7) is preferably a C1-C6alkyl group.

The alicyclic hydrocarbon group represented by R^(a6) or R^(a7) haspreferably 8 or less, more preferably 6 or less of carbon atoms. “m1” ispreferably an integer of 0 to 3, and more preferably 0 or 1. “n1” ispreferably an integer of 0 to 3, and more preferably 0 or 1. “n1′” ispreferably 0 or 1.

The structural unit (a1-0) is preferably one represented by any one ofthe following formulae, and more preferably one represented by any oneof formulae (a1-0-1) to (a1-0-10).

Other examples of the structural unit (a1-0) include those representedby the above-mentioned formulae in which a methyl group bonded to itsmain chain has been replaced by a hydrogen atom.

Examples of the structural unit (a1-1) include those derived from amonomer (a1-1) as recited in JP2010-204646A1. Preferred are thestructural units represented by of formulae (a1-1-1) to (a1-1-8)

As the structural unit (a1-2), preferred are those represented byformulae (a1-2-1) to (a1-2-12), more preferred are those represented byformulae (a1-2-3), (a1-2-4), (a1-2-9) and (a1-2-10), more preferred arethose represented by formulae (a1-2-3) and (a1-2-9).

When the resin (A) has at least one of the structural units (a1-0),(a1-1) and (a1-2), the content of the structural unit in the resin isusually 10 to 95% by mole, preferably 15 to 90% by mole, and morepreferably 20 to 85% by mole based on all the structural units of theresin (A).

Another example of the structural unit (a1) includes a structural unitrepresented by the formula (a1-5).

In the formula (a1-5), R^(a)s represents a hydrogen atom, a halogen atomor a C1-C6 alkyl group that may have a halogen atom,

Z^(a1) represent a single bond or *—(CH₂)_(h3)—CO-L⁵⁴-, where h3represents an integer of 1 to 4, * represents a binding site to L⁵¹, andL⁵⁴ represents —O— or —S—,

L⁵¹, L⁵² and L⁵³ each independently represent —O— or —S—,

“s1” represents an integer of 1 to 3, and

“s1′” represents an integer of 0 to 3.

The structural unit represented by the formula (a1-5) is sometimesreferred to as “structural unit (a1-5)”.

R^(a8) is preferably a hydrogen atom, a methyl group or atrifluoromethyl group. L⁵¹ is preferably —O—.

L⁵² and L⁵³ are independently preferably —O— or —S—, and more preferablyone is —O— and the other is —S—.

“s1” is preferably 1. “s1′” is preferably an integer of 0 to 2.

Z^(a1) is preferably a single bond or *—CH₂—CO—O— where * represents abinding site to L⁵¹

Examples of the monomer from which the structural unit (a1-5) is derivedinclude the monomers described in JP2010-61117A1. Among these, themonomers are preferably the following monomers represented by formula(a1-5-1) to formula (a1-5-4), and more preferably monomers representedby formula (a1-5-1) and formula (a1-5-2).

When the resin (A) has a structural unit (a1-5), the content of thestructural unit is usually 1 to 50% by mole, preferably 3 to 45% by moleand more preferably 5 to 40% by mole based on all the structural unitsof the resin.

Examples of the structural unit (a1) further include the followingstructural units.

When the resin (A) has at least one of the structural units (a1-3-1), to(a1-3-7), the content of the structural unit in the resin is usually 10to 95% by mole, preferably 15 to 90% by mole, and more preferably 20 to85% by mole based on all the structural units of the resin (A).

Examples of the structural unit (a1) having the group represented byformula (2) include a structural unit represented by formula (a1-4). Thestructural unit is sometimes referred to as “structural unit (a1-4)”.

In the formula, R^(a32) represents a hydrogen atom, a halogen atom or aC1-C6 alkyl group that may have a halogen atom,

R^(a33) in each occurrence independently represent a halogen atom, ahydroxy group, a C1-C6 alkyl group, a C1-C6 alkoxy group, a C2-C4 acylgroup, a C2-C4 acyloxy group, an acryloyloxy group or methacryloyloxygroup,

“la” represents an integer 0 to 4,

R^(a34) and R^(a35) each independently represent a hydrogen atom or aC1-C12 hydrocarbon group; and

R^(a3) represents a C1-C20 hydrocarbon group, or R^(a35) and R^(a36) maybe bonded together with a C—O bonded thereto to form a divalent C3-C20heterocyclic group, and a methylene group contained in the hydrocarbongroup or the divalent heterocyclic group may be replaced by an oxygenatom or a sulfur atom.

Examples of the alkyl group of R^(a32) and R^(a33) include methyl,ethyl, propyl, isopropyl, butyl, pentyl and hexyl groups. The alkylgroup is preferably a C1-C4 alkyl group, and more preferably a methylgroup or an ethyl group, and still more preferably a methyl group.

Examples of the halogen atom of R^(a32) and R^(a33) include a fluorine,chlorine, bromine and iodine atoms.

Examples of the alkyl group that may have a halogen atom includetrifluoromethyl, difluoromethyl, methyl, perfluoroethyl,1,1,1-trifluoroethyl, 1,1,2,2-tetrafluoroethyl, ethyl, perfluoropropyl,1,1,1,2,2-pentafluoropropyl, propyl, perfluorobutyl,1,1,2,2,3,3,4,4-octafluorobutyl, butyl, perfluoropentyl,1,1,1,2,2,3,3,4,4-nonafluoropentyl, n-pentyl, n-hexyl andn-perfluorohexyl groups.

Examples of an alkoxy group include methoxy, ethoxy, propoxy, butoxy,pentyloxy and hexyloxy groups. The alkoxy group is preferably a C1-C4alkoxy group, more preferably a methoxy group or an ethoxy group, andstill more preferably a methoxy group. Examples of the acyl groupinclude acetyl, propionyl and butyryl groups. Examples of the acyloxygroup include acetyloxy, propionyloxy and butyryloxy groups. Examples ofthe hydrocarbon group for R^(a34) and R^(a35) are the same examples asdescribed in R^(a1′) to R^(a2′) in the formula (2).

Examples of hydrocarbon group for R^(a36) include a C1-C18 alkyl group,a C3-C18 alicyclic hydrocarbon group, a C6-C18 aromatic hydrocarbongroup or a group formed by combining thereof.

In the formula (a1-4), R^(a32) is preferably a hydrogen atom. R^(a33) ispreferably a C1-C4 alkoxy group, more preferably a methoxy group or anethoxy group, and still more preferably a methoxy group. “la” ispreferably 0 or 1, and more preferably 0. R^(a34) is preferably ahydrogen atom. R^(a35) is preferably a C1-C12 hydrocarbon group, andmore preferably a methyl group or an ethyl group.

The hydrocarbon group for R^(a36) is preferably a C1-C18 alkyl group, aC3-C18 alicyclic hydrocarbon group, a C6-C18 aromatic hydrocarbon groupor a combination thereof, and more preferably a C1-C18 alkyl group, aC3-C18 alicyclic hydrocarbon group or a C7-C18 aralkyl group. The alkylgroup and the alicyclic hydrocarbon group for R^(a36) are preferablyunsubstituted. When the aromatic hydrocarbon group of R^(a36) has asubstituent, the substituent is preferably a C6-C10 aryloxy group.

Examples of the structural unit (a1-4) include those derived from themonomers described in JP2010-204646A1. Among them, the structural unitis preferably the following ones represented by formula (a1-4-1) toformula (a1-4-8), and more preferably the structural units representedby formula (a1-4-1) to formula (a1-4-5).

When the resin (A) has the structural unit (a1-4), the proportionthereof is preferably 10% by mole to 95% by mole, more preferably 15% bymole to 90% by mole, and still more preferably 20% by mole to 85% bymole, based on the all the structural units of the resin (A) (100% bymole).

The resin (A) may further have a structural unit having no acid-labilegroup.

The structural unit having no acid-labile group preferably has a hydroxygroup or lactone group. The structural unit having not acid-labile groupbut a hydroxy group is sometimes referred to as “structural unit (a2)”.The structural unit having not acid-labile group but a lactone group issometimes referred to as “structural unit (a3)”.

The resin (A) which has a structural unit (a2) or (a3) can give aphotoresist composition capable of providing a photoresist pattern withimproved resolution and adhesiveness to a substrate.

The structural unit (a2) may have an alcoholic hydroxy group or aphenolic-hydroxy group.

When KrF excimer laser (wavelength: 248 nm) lithography system, or ahigh energy laser such as electron beam and extreme ultraviolet is usedas an exposure system, preferred is a resin which has a structural unit(a2) having a phenolic-hydroxy group.

When ArF excimer laser (wavelength: 193 nm) is used as an exposuresystem, preferred is a resin which has the structural unit (a2) havingan alcoholic hydroxy group.

Examples of the structural unit (a2) having a phenolic-hydroxy groupinclude a structural unit represented by formula (a2-0):

wherein R^(a50) represents a hydrogen atom, a halogen atom or a C1-C6alkyl group in which a hydrogen atom can be replaced by a halogen atom,R^(a51) represents a halogen atom, a hydroxy group, a C1-C6 alkyl group,a C1-C6 alkoxy group, a C1-C6 alkylcarbonyl group, a C2-C4alkylcarbonyloxy group, an acryloyloxy group or methacryloyloxy group,A^(a50) represents a single bond or *—X^(a51)-(A^(a52)-X^(a52))_(nb)— inwhich * represents a binding site to the carbon atom attached toR^(a50), A^(a52) represents a C1-C6 alkanediyl group, X^(a51) andX^(a52) each independently represent —O—, —CO—O— or —O—CO—, nbrepresents 0 or 1, and mb represents an integer of 0 to 4.

Examples of the halogen atom for R^(a50) include fluorine, chlorine,bromine and iodine atoms.

As to R^(a50), examples of the alkyl group in which a hydrogen atom canbe replaced by a halogen atom include a trifluoromethyl group, adifluoromethyl group, a methyl group, a perfluoroethyl group, a1,1,1-trifluoroethyl group, a 1,1,2,2-tetrafluoroethyl group, an ethylgroup, a perfluoropropyl group, a 1,1,1,2,2-pentafluoropropyl group, apropyl group, a perfluorobutyl group, a 1,1,2,2,3,3,4,4-octafluorobutylgroup, a butyl group, perfluoropentyl group, a1,1,1,2,2,3,3,4,4-nonafluoropentyl group, a pentyl group, a hexyl groupand a perfluorohexyl group. R^(a50) is preferably a hydrogen atom or aC1-C4 alkyl group, more preferably a hydrogen atom, a methyl group or anethyl group, still more preferably a hydrogen atom or a methyl group.

As to R^(a51), examples of an alkyl group include methyl, ethyl,n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, pentyl and hexylgroups.

As to R^(a51), examples of an alkoxy group include a methoxy group, anethoxy group, a propoxy group, an isopropoxy group, a butoxy group, asec-butoxy group and a tert-butoxy group. The alkoxy group representedby R^(a51) is preferably a hydrogen atom or a C1-C4 alkoxy group, morepreferably a methoxy group or an ethoxy group, still more preferably amethoxy group.

As to R^(a51), examples of an alkylcarbony group include an acetylgroup, a propionyl group and a butyryl group.

As to R^(a51), examples of an alkylcarbonyloxy group include anacetyloxy group, a propionyloxy group and a butyryloxy group.

R^(a51) is a methyl group.

Examples of the group represented by *—X^(a51)-(A^(a52)-X^(a52))_(nb)—include —O—, —CO—O—, —O—CO—, *—CO—O-A^(a52)-CO—O—, —O—CO-A^(a52)-O—,—O-A^(a52)-CO—O—, *—CO—O-A^(a2)-O—CO—, —O—CO-A^(a52)-O—CO—. Among them,*—CO—O—, *—CO—O-A^(a52)-CO—O— and *—O-A^(a52)-CO—O— are preferred.

mb represents preferably 0, 1 or 2, more preferably 0 or 1, and stillmore preferably 0.

In formula (a2-0), a hydroxyl group is preferably bonded to o-positionor p-position, more preferably bonded to p-position.

Examples of the structural unit represented by formula (a2-0) includethose derived from a monomer recited in JP2010-204634A1 andJP2012-12577A1.

Examples of the structural unit represented by the formula (a2-0)preferably include those represented by formulae (a2-0-1) to (a2-0-8),and more preferably those represented by formulae (a2-0-1), (a2-0-2),(a2-0-3) and (a2-0-4).

When the resin (A) further has the structural unit (a2) having aphenolic-hydroxy group, the proportion thereof is preferably 5 to 95% bymole, more preferably 10 to 80% by mole, and still more preferably 15 to80% by mole, based on all the structural units of the resin (A).

Preferred examples of the structural unit (a2) having an alcoholichydroxy group include a structural unit represented by the formula(a2-1):

wherein R^(a14) represents a hydrogen atom or a methyl group, R^(a15)and R^(a16) each independently represent a hydrogen atom, a methyl groupor a hydroxy group, L^(a3) represents an oxygen atom or*—O—(CH₂)_(k2)—CO—O— in which * represents a binding site to —CO—, andk2 represents an integer of 1 to 7, and o1 represents an integer of 0 to10.

In the formula (a2-1), L^(a3) is preferably an oxygen atom or*—O—(CH₂)_(f2)—CO—O— in which * represents a binding site to —CO—, andf2 represents an integer of 1 to 4, is more preferably an oxygen atom or*—O—CH₂—CO—O—, and is still more preferably an oxygen atom.

R^(a14) is preferably a methyl group.

R^(a15) is preferably a hydrogen atom.

R^(a16) is preferably a hydrogen atom or a hydroxy group.

o1 is preferably 0, 1, 2 or 3 and is more preferably 0 or 1.

Examples of the monomer from which the structural unit represented bythe formula (a2-1) is derived include those mentioned inJP2010-204646A1. Examples of the structural unit represented by theformula (a2-1) preferably include those represented by formulae(a2-1-1), (a2-1-2), (a2-1-3), (a2-1-4), (a2-1-5) and (a2-1-6), and morepreferably those represented by formulae (a2-1-1), (a2-1-2), (a2-1-3)and (a2-1-4), still more preferably those represented by formulae(a2-1-1) and (a2-1-3).

When the resin (A) further has the structural unit represented by theformula (a2-1), the content of the structural unit represented by theformula (a2-1) is usually 1 to 45% by mole and preferably 1 to 40% bymole, more preferably 1 to 35% by mole, still more preferably 2 to 20%by mole, still further more preferably 2 to 5% by mole, based on all thestructural units of the resin (A).

In the structural unit (a3), examples of the lactone ring include amonocyclic lactone ring such as β-propiolactone ring, γ-butyrolactonering and δ-valerolactone ring, and a condensed ring formed from amonocyclic lactone ring and the other ring. Among them, preferred areγ-butyrolactone ring and a condensed lactone ring formed fromγ-butyrolactone ring and another ring.

Preferable examples of the structural unit (a3) include thoserepresented by the formulae (a3-1), (a3-2), (a3-3) and (a3-4):

wherein L^(a4), L^(a5) and L^(a6) each independently represent —O— or*—O—(CH₂)_(k3)—CO—O— in which * represents a binding site to —CO— and k3represents an integer of 1 to 7,

L^(a7) represents a single bond, —O—, *—O-L^(a8)-O—, *—O-L^(a8)-CO—O—,*—O-L^(a8)-CO—O-L^(a9)-CO—O—, or *—O-L^(a8)-O—CO-L^(a9)-O—; * representsa binding site to a carbonyl group, L^(a8) and L^(a9) each represent aC1-C6 alkanediyl group,

R^(a8), R^(a9) and R^(a2°) each independently represent a hydrogen atomor a methyl group,

R^(a2) represents a C1-C4 aliphatic hydrocarbon group, R^(a22), R^(a23)and R^(a25) are independently in each occurrence a carboxyl group, acyano group or a C1-C4 aliphatic hydrocarbon group, R^(a24) represents ahydrogen atom, a halogen atom or a C1-C6 alkyl group optionally having ahalogen atom, p1 represents an integer of 0 to 5, q1 and r1 eachindependently represent an integer of 0 to 3, and w represents aninteger of 0 to 8.

Examples of the aliphatic hydrocarbon group for R^(a21), R^(a22),R^(a23) and R^(a25) include an alkyl group such as methyl, ethyl,n-propyl, isopropyl, n-butyl, sec-butyl and tert-butyl groups.

Examples of the alkanediyl group of L^(a8) and L^(a9) include methylene,ethylene, propane-1,3-diyl, propane-1,2-diyl, butane-1,4-diyl,pentane-1,5-diyl, hexane-1,6-diyl, butane-1,3-diyl,2-methylpropane-1,3-diyl, 2-methylpropane-1,2-diyl, pentane-1,4-diyl and2-methylbutane-1,4-diyl groups.

L^(a4), L^(a5) and L^(a6) each independently represent preferably —O— or*—O—(CH₂)_(d1)—CO—O— in which * represents a binding site to —CO— and d1represents an integer of 1 to 4, and more preferably —O— and*—O—CH₂—CO—O—, and still more preferably —O—.

Preferably, R^(a18), R^(a19) and R^(a20) are independently in eachoccurrence a methyl group.

Preferably, R^(a22) and R^(a23) are independently in each occurrence acarboxyl group, a cyano group or a methyl group.

p1, q1, r1 and w are independently in each occurrence preferably aninteger of 0 to 2, and more preferably 0 or 1.

Examples of the halogen atom for R^(a24) include fluorine, chlorine,bromine and iodine atoms.

Examples of the alkyl group for R^(a24) include methyl, ethyl, n-propyl,isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl and n-hexyl groups.The alkyl group is preferably a C1-C4 alkyl group, more preferably amethyl group or an ethyl group.

Examples of the alkyl group having a halogen atom for R^(a24) includetrifluoromethyl, perfluoroethyl, perfluoropropyl, perfluoro-isopropyl,perfluorobutyl, perfluoro-sec-butyl, perfluoro-tert-butyl,perfluoropentyl, perfluorohexyl, trichloromethyl, tribromomethyl andtriiodomethyl groups.

R^(a24) is preferably a hydrogen atom or a C1-C4 alkyl group, morepreferably a hydrogen atom, a methyl group or an ethyl group, and stillmore preferably a hydrogen atom or a methyl group.

L^(a7) represents preferably a single bond or *-L^(a8)-CO—O—, and morepreferably a single bond, *—CH₂—CO—O— or *—C₂H₄—CO—O—.

The structural unit represented by formula (a3-4) is preferably onerepresented by formula (a3-4)′.

In formula (a3-4)′, R^(a24) and L^(a7) are as defined above.

Examples of the monomers from which the structural unit (a3) is derivedinclude those mentioned in JP2010-204646A1, JP2010-122294A1, andJP2010-41274A1. Examples of the structural unit (a3) include preferablythose represented by the formulae (a3-1-1) to (a3-1-4), the formulae(a3-2-1) to (a3-2-4), the formulae (a3-3-1) to (a3-3-4), and theformulae (a3-4-1) to (a3-4-12), more preferably those represented by theformulae (a3-1-1), (a3-1-2), (a3-2-1), (a3-2-3), (a3-2-4), (a3-4-1) to(a3-4-12), still more preferably those represented by the formulae(a3-4-1) to (a3-4-12), and furthermore preferably those represented bythe formulae (a3-4-1) to (a3-4-6).

Examples of the structural unit (a3) further include those representedby formulae (a3-4-1) to (a3-4-12) in which a methyl group has beenreplaced by a hydrogen atom.

When the resin (A) has the structural unit (a3), the total content ofthe structural unit (a3) is usually 5 to 70% by mole, preferably 10 to65% by mole, and more preferably 10 to 60% by mole, based on all thestructural units of the resin (A).

When the resin (A) has the structural unit (a3-1), (a3-2), (a3-3) or(a3-4), each content of them is usually 5 to 60% by mole, preferably 5to 50% by mole, and more preferably 10 to 50% by mole, based on all thestructural units of the resin (A).

The resin (A) may further have a structural unit other than thestructural units (a1), (a2) and (a3). The structural unit other than thestructural units (a1), (a2) and (a3) is sometimes referred to as the“structural unit (t)”.

Examples of the structural unit (t) include a structural unit having ahalogen atom such as a fluorine atom and a structural unit which has ahydrocarbon group having no acid-labile group.

As to the structural unit (t), examples of the structural unit having ahalogen atom, which structural unit is sometimes referred to as“structural unit (a4)”, include a structural unit represented by formula(a4-0).

In the formula (a4-0), R represents a hydrogen atom or a methyl group,L⁵ represents a single bond or a C1-C4 saturated aliphatic hydrocarbongroup, L³ represents a C1-C8 perfluoroalkanediyl group, or a C3-C12perfluorocycloalkanediyl group, and R⁶ represents a hydrogen atom or afluorine atom.

Examples of the saturated aliphatic hydrocarbon group for L⁵ includeC1-C4 alkanediyl group, i.e., a linear alkanediyl group such asmethylene, ethylene, propane-1,3-diyl, and butane-1,4-diyl groups; and abranched alkanediyl group such as ethane-1,1-diyl, propane-1,2-diyl,butane-1,3-diyl, 2-methylpropane-1,3-diyl and 2-methylpropane-1,2-diylgroups.

L⁵ is preferably a single bond, methylene or ethylene group, and morepreferably a single bond or a methylene group.

Examples of the perfluoroalkanediyl group for L³ includedifluoromethylene, perfluoroethylene, perfluoropropane-1,3-diyl,perfluoropropane-1,2-diyl, perfluoropropane-2,2-diyl,perfluorobutane-1,4-diyl, perfluorobutane-2,2-diyl,perfluorobutane-1,2-diyl, perfluoropentane-1,5-diyl,perfluoropentane-2,2-diyl, perfluoropentane-3,3-diyl,perfluorohexane-1,6-diyl, perfluorohexane-2,2-diyl,perfluorohexane-3,3-diyl, perfluoroheptane-1,7-diyl,perfluoroheptane-2,2-diyl, perfluoroheptane-3,4-diyl,perfluoroheptane-4,4-diyl, perfluorooctan-1,8-diyl,perfluorooctan-2,2-diyl, perfluorooctan-3,3-diyl andperfluorooctan-4,4-diyl groups.

Examples of the perfluorocycloalkanediyl group for L³ includeperfluorocyclohexanediyl, perfluorocyclopentanediyl,perfluorocycloheptanediyl and perfluoroadamantanediyl groups.

L³ is preferably a C1-C6 perfluoroalkanediyl group, more preferably aC1-C3 perfluoroalkanediyl group.

Examples of the structural unit represented by formula (a4-0) includethose as follow.

Examples of the structural unit (a4) include those represented byformula (a4-1):

wherein R^(a41) represents a hydrogen atom or a methyl group,

R^(a42) represents an optionally substituted C1-C20 hydrocarbon groupwhere a methylene group may be replaced by an oxygen atom or a carbonylgroup, and

A^(a41) represents an optionally substituted C1-C6 alkanediyl group or agroup represented by formula (a-g1):

**-A^(a42)X^(a41)-A^(a43)_(s)X^(a42)-A^(a44)-*  (a-g1)

wherein s represents 0 or 1,

A^(a42) and A^(a44) each independently represent an optionallysubstituted C1-C5 divalent aliphatic hydrocarbon group,

A^(a43) represents a single bond or an optionally substituted C1-C5divalent aliphatic hydrocarbon group, and

X^(a41) and X^(a42) each independently represent —O—, —CO—, —CO—O— or—O—CO—,

provided that the total number of the carbon atoms contained in thegroup of A^(a42), A^(a43), A^(a44), X^(a41) and X^(a42) is 6 or less, atleast one of A^(a41) and R^(a42) has a halogen atom as a substituent,and

* and ** represent a binding site, and * represents a binding site to—O—CO—R^(a42).

The hydrocarbon group for R^(a42) may be a chain aliphatic hydrocarbongroup, a cyclic aliphatic hydrocarbon group, an aromatic hydrocarbongroup, or a combination thereof.

The chain aliphatic hydrocarbon group and the cyclic aliphatichydrocarbon group may have a carbon-carbon unsaturated bond, and ispreferably a chain and a cyclic saturated aliphatic hydrocarbon group.Examples of the saturated aliphatic hydrocarbon group include a linearor branched alkyl group, a monocyclic or polycyclic alicyclichydrocarbon group, and an aliphatic hydrocarbon group formed bycombining the alkyl group and the alicyclic hydrocarbon group.

Examples of the chain aliphatic hydrocarbon group include an alkyl groupsuch as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl,decyl, dodecyl and hexadecyl groups.

Examples of the alicyclic hydrocarbon group include a cycloalkyl groupsuch as cyclopentyl, cyclohexyl, cycloheptyl and cyclooctyl groups; andpolycyclic hydrocarbon groups such as decahydronaphtyl, adamantyl andnorbornyl groups as well as groups below. * represents a binding site.

Examples of the aromatic hydrocarbon group include an aryl group such asphenyl, naphthyl, anthryl, biphenyl, phenanthryl and fluorenyl groups.

The hydrocarbon group for R^(a42) is preferably a chain aliphatichydrocarbon group, a cyclic aliphatic hydrocarbon group, and acombination thereof. The hydrocarbon group may have a carbon-carbonunsaturated bond, is preferably a chain saturated aliphatic hydrocarbongroup, a cyclic saturated aliphatic hydrocarbon group, and a combinationthereof.

Examples of the substituent for R^(a42) include a halogen atom and agroup represented by formula (a-g3):

*—X^(a43)-A^(a45)  (a-g3)

wherein X^(a43) represent an oxygen atom, a carbonyl group, acarbonyloxy group or an oxycarbonyl group,

A^(a45) represents a C1-C17 aliphatic hydrocarbon group that has ahalogen atom, and * represents a binding site.

Examples of the halogen atom include fluorine, chlorine, bromine oriodine atom, and preferably a fluorine atom.

Examples of the aliphatic hydrocarbon group for A^(a45) include the sameones as those for R^(a42).

R^(a42) is preferably an aliphatic hydrocarbon group that may have ahalogen atom, and more preferably an alkyl group having a halogen atomand/or an aliphatic hydrocarbon group having the group represented bythe formula (a-g3).

When R^(a42) is an aliphatic hydrocarbon group having a halogen atom, analiphatic hydrocarbon group having a fluorine atom is preferred, aperfluoroalkyl group or a perfulorocycloalkyl group are more preferred,a C1-C6 perfluoroalkyl group is still more preferred, a C1-C3perfluoroalkyl group is particularly preferred.

Examples of the perfluoroalkyl group include perfluoromethyl,perfluoroethyl, perfluoropropyl, perfluorobutyl, perfluoropentyl,perfluorohexyl, perfluoroheptyl and perfluorooctyl groups.

Examples of the perfluorocycloalkyl group include perfluorocyclohexylgroup.

The aliphatic hydrocarbon group having the group represented by theformula (a-g3) is more preferably a group represented by formula (a-g2):

*-A^(a46)-X^(a44)-A^(a47)  (a-g2)

wherein A^(a46) represents a C1-C17 aliphatic hydrocarbon group that mayhave a halogen atom,

X^(a44) represent a carbonyloxy group or an oxycarbonyl group,

A^(a47) represents a C1-C17 aliphatic hydrocarbon group that may have ahalogen atom,

provided that the total number of the carbon atoms contained in thegroup of A^(a46), X^(a44) and A^(a47) is 18 or less,

at least one of A^(a46) and A^(a47) has a halogen atom, and

* represents a binding site to a carbonyl group.

The aliphatic hydrocarbon group for A^(a46) has preferably 1 to 6 carbonatoms, more preferably 1 to 3, carbon atoms.

The aliphatic hydrocarbon group for A^(a47) has preferably 4 to 15carbon atoms, more preferably 5 to 12 carbon atoms. A^(a47) is morepreferably a cyclohexyl group or an adamantyl group.

Preferred examples of *-A^(a46)-X^(a44)-A^(a47) include the followingones.

Examples of the alkanediyl group for A^(a4) include a linear alkanediylgroup such as methylene, ethylene, propane-1,3-diyl, butane-1,4-diyl,pentane-1,5-diyl and hexane-1,6-diyl groups;

a branched alkanediyl group such as propane-1,2-diyl, butan-1,3-diyl,2-methylpropane-1,2-diyl, l-methylbutane-1,4-diyl,2-methylbutane-1,4-diyl groups.

Examples of the substituent on the alkanediyl group for A^(a41) includea hydroxy group and a C1-C6 alkoxy group.

A^(a41) is preferably a C1-C4 alkanediyl group, more preferably a C2-C4alkanediyl group, and still more preferably ethylene group.

In the group represented by the formula (a-g1) (which is sometimesreferred to as “group (a-g1)”), examples of the aliphatic hydrocarbongroup for A^(a42), A^(a43) and A^(a44) include methylene, ethylene,propane-1,3-diyl, propane-1,2-diyl, butane-1,4-diyl,l-methylpropane-1,3-diyl, 2-methylpropane-1,3-diyl and2-methylpropane-1,2-diyl groups.

Examples of the substituent on the aliphatic hydrocarbon group forA^(a42), A^(a43) and A^(a44) include a hydroxy group and a C1-C6 alkoxygroup. s is preferably 0.

Examples of the group (a-g1) in which X^(a42) represents an oxygen atominclude the following ones. In the formulae, * and ** each represent abinding site, and ** represents a binding site to —O—CO—R^(a42)

Examples of the group (a-g1) in which X^(a42) represents a carbonylgroup include the following ones. In the formulae, * and ** are asdefined above.

Examples of the group (a-g1) in which X^(a42) represents a carbonyloxygroup include the following ones. In the formulae, * and ** are asdefined above.

Examples of the group (a-g1) in which X^(a42) represents an oxycarbonylgroup include the following ones. In the formulae, * and ** are asdefined above.

The structural unit represented by the formula (a4-1) is preferably astructural unit represented by formula (a4-2):

wherein R^(f1) represents a hydrogen atom or a methyl group,

A^(f1) represent a C1-C6 alkanediyl group, and

R^(f2) represents a C1-C10 hydrocarbon group that has a fluorine atom.

Examples of the alkanediyl group for A^(f1) include a linear alkanediylgroup such as methylene, ethylene, propane-1,3-diyl, propane-1,2-diyl,butane-1,4-diyl, pentane-1,5-diyl and hexane-1,6-diyl groups; a branchedalkanediyl group such as 1-methylpropane-1,3-diyl,2-methylpropane-1,3-diyl, 2-methylpropane-1,2-diyl,1-methylbutane-1,4-diyl and 2-methylbutane-1,4-diyl groups.

Examples of the hydrocarbon group for R^(f2) include an aliphatichydrocarbon group and an aromatic hydrocarbon group. The aliphatichydrocarbon group includes chain and cyclic groups, and a combinationthereof. The aliphatic hydrocarbon group is preferably an alkyl groupand a cyclic aliphatic hydrocarbon group.

Examples of the alkyl group include methyl, ethyl, n-propyl, isopropyl,n-butyl, sec-butyl, tert-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl and2-ethylhexyl groups.

Examples of the cyclic aliphatic hydrocarbon group include any of amonocyclic group and a polycyclic group. Examples of the monocyclicalicyclic hydrocarbon group include a cycloalkyl group such ascyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, methylcyclohexyl,dimethylcyclohexyl, cycloheptyl, cyclooctyl, and cyclodecyl groups.Examples of the polycyclic hydrocarbon groups includesdecahydronaphthyl, adamantyl, 2-alkyladamantane-2-yl,1-(adamantane-1-yl)alkane-1-yl, norbornyl, methylnorbornyl and isobornylgroups.

Examples of the hydrocarbon group having a fluorine atom for R^(f2)include an alkyl group having a fluorine atom and an alicyclichydrocarbon group having a fluorine atom.

Specific examples of an alkyl group having a fluorine atom include afluorinated alkyl group such as difluoromethyl, trifluoromethyl,1,1-difluoroethyl, 2,2-difluoroethyl, 2,2,2-trifluoroethyl,perfluoroethyl, 1,1,2,2-tetrafluoropropyl, 1,1,2,2,3,3-hexafluoropropyl,perfluoroethylmethyl, 1-(trifluoromethyl)-1,2,2,2-tetrafluoroethyl,perfluoropropyl, 1-(trifluoromethyl)-2,2,2-trifluoroethyl,1,1,2,2-tetrafluorobutyl, 1,1,2,2,3,3-hexafluorobutyl,1,1,2,2,3,3,4,4-octafluorobutyl, perfluorobutyl,1,1-bis(trifluoro)methyl-2,2,2-trifluoroethyl, 2-(perfluoropropyl)ethyl,1,1,2,2,3,3,4,4-octafluoropentyl, perfluoropentyl,1,1,2,2,3,3,4,4,5,5-decafluoropentyl,1,1-bis(trifluoromethyl)-2,2,3,3,3-pentafluoropropyl,2-(perfluorobutyl)ethyl, 1,1,2,2,3,3,4,4,5,5-decafluorohexyl,1,1,2,2,3,3,4,4,5,5,6,6-dodeca fluorohexyl, perfluoropentylmethyl andperfluorohexyl groups.

Examples of the alicyclic hydrocarbon group having a fluorine atominclude a fluorinated cycloalkyl group such as perfluorocyclohexyl andperfluoroadamantyl groups.

In the formula (a4-2), A^(f1) is preferably a C2-C4 alkanediyl group,and more preferably an ethylene group.

R^(f2) is preferably a C1-C6 fluorinated alkyl group.

Another preferred example of the structural unit represented by theformula (a4-1) includes one represented by formula (a4-3):

In formula, R^(f11) represents a hydrogen atom or a methyl group.

A^(f11) represents a C1-C6 alkanediyl group.

A^(f13) represents a C1-C18 chain or alicyclic hydrocarbon group whichmay have a fluorine atom.

X^(f12) represents a carbonyloxy group or an oxycarbonyl group.

A^(f14) represents a C1-C17 chain or alicyclic hydrocarbon group whichmay have a fluorine atom, provided that one or both of A^(f13) and

A^(f14) represents a fluorine-containing aliphatic hydrocarbon group.Examples of the alkanediyl group represented by A^(f11) include those asreferred to for A^(f11).

A^(f13) further includes combined groups of chain hydrocarbon groups andalicyclic hydrocarbon groups.

As to A^(f13), the chain or alicyclic hydrocarbon group which may have afluorine atom is preferably a divalent saturated chain hydrocarbon groupwhich may have a fluorine atom, more preferably a perfluoroalkanediylgroup.

Examples of the divalent chain saturated hydrocarbon group which mayhave a fluorine atom include an alkanediyl group such as a methylenegroup, an ethylene group, a propanediyl group, a butanediyl group andpentanediyl group; and a perfluoroalkanediyl group such as adifluoromethylene group, a perfluoroethylene group, aperfluoropropanediyl group, a perfluorobutanediyl group andperfluoropentanediyl group.

The divalent cyclic saturated hydrocarbon group which may have afluorine atom may be a divalent monocyclic or polycyclic group. Examplesof the divalent monocyclic hydrocarbon group which may have a fluorineatom include a cyclohexanediyl group and a perfluorocyclohexanediylgroup.

Examples of the divalent polycyclic hydrocarbon group which may have afluorine atom include an adamantanediyl group, norbornanediyl group, anda perfluoroadamantanediyl group.

In the group represented by A^(f4), the aliphatic hydrocarbon groupincludes chain saturated hydrocarbon groups, cyclic saturatedhydrocarbon groups and combined groups of these saturated hydrocarbongroups.

As to A^(f14), the chain or alicyclic hydrocarbon group which may have afluorine atom is preferably a saturated aliphatic hydrocarbon groupwhich may have a fluorine atom, more preferably a perfluoroalkanediylgroup.

Examples of the chain hydrocarbon group which may have a fluorine atominclude a trifluoromethyl group, a fluoromethyl group, a methyl group, aperfluoroethyl group, a 1,1,1-trifluoroethyl group, a1,1,2,2-tetrafluoroethyl group, an ethyl group, a perfluoropropyl group,a 1,1,1,2,2-pentafluoropropyl group, propyl group, a perfluorobutylgroup, 1,1,2,2,3,3,4,4-octafluorobutyl group, a butyl group, aperfluoropentyl group, 1,1,1,2,2,3,3,4,4-nonafluoropentyl group, apentyl group, a hexyl group, a perfluorohexyl group, a heptyl group, aperfluoroheptyl group, an octyl group and a perfluorooctyl group.

The alicyclic hydrocarbon group which may have a fluorine atom may bemonocyclic or polycyclic group.

Examples of the monovalent monocyclic hydrocarbon group which may have afluorine atom include a cyclopropyl group, cyclopentyl group, cyclohexylgroup, and perfluorocyclohexyl group.

Examples of the polycyclic hydrocarbon group which may have a fluorineatom include an adamantyl group, a norbornyl group, and aperfluoroadamantyl group.

Examples of the combined groups of the above-mentioned chain andalicyclic hydrocarbon groups include a cyclopropylmethyl group, acyclobutylmethyl group, an adamantylmethyl group, a norbornylmethylgroup and a perfluoroadamantylmethyl group.

In formula (a4-3), A^(f11) is preferably an ethylene group.

The chain or alicyclic hydrocarbon group represented by A^(f13) haspreferably 6 or less, more preferably 2 to 3, of carbon atoms.

The chain or alicyclic hydrocarbon group represented by A^(f14) haspreferably 3 to 12, more preferably 3 to 10, of carbon atoms. A^(f14)has preferably a C3-C12 alicyclic hydrocarbon group, more preferably acyclopropylmethyl group, a cyclopentyl group, a cyclohexyl group, anorbornyl group or an adamantyl group.

Examples of the structural unit represented by formula (a4-2) includestructural units represented by formula (a4-1-1) to formula (a4-1-11)and the structural units represented by these formulae in which a methylgroup has been replaced by a hydrogen atom.

Examples of the structural unit represented by formula (a4-3) includestructural units represented by the following formulae and thestructural units represented by these formulae in which a methyl grouphas been replaced by a hydrogen atom.

Another example of the structural unit represented by the formula (a4-1)includes one represented by formula (a4-4):

In formula, R^(f21) represents a hydrogen atom or a methyl group.

A^(f21) represents —(CH₂)_(j1)—, —(CR₂)_(j2)—O—(CH₂)_(j3)— or—(CH₂)_(j4)—C(═O)—O—(CH₂)_(j5)—, and j1 to j5 each independentlyrepresent an integer of 1 to 6.

R^(f22) represents a C1-C10 hydrocarbon group which has a fluorine atom.Examples of the hydrocarbon group represented by R^(f22) include thoseas referred to for R^(f2).

R^(f22) is preferably a C1-C10 fluorinated alkyl group or a C3-C10fluorinated cycloalkyl group, more preferably a C1-C10 fluorinated alkylgroup, and still more preferably a C1-C6 fluorinated alkyl group.

In formula, A^(f21) represents preferably —(CH₂)_(j1)—, more preferablya methylene group or an ethylene group, and still more preferably amethylene group.

Examples of the structural unit represented by formula (a4-4) furtherinclude the following ones and those represented by the followingformulae in which a methyl group has been replaced by a hydrogen atom.

When Resin (A) has the structural unit (a4), the content thereof isusually 1 to 20% by mole, preferably 2 to 15% by mole, and morepreferably 3 to 10% by mole, based on all the structural units of theresin (A)

The structural unit which has a hydrocarbon group having no acid-labilegroup, which is sometimes referred to as the “structural unit (a5)”, mayhave a linear, branched or cyclic hydrocarbon group, preferably analicyclic hydrocarbon group.

Examples of the structural unit (a5) include one represented by formula(a5-1):

where R⁵¹ represents a hydrogen atom or a methyl group;

R⁵² represents a C3-C18 alicyclic hydrocarbon group, provided that thealicyclic hydrocarbon group has no substituent on the carbon atom bondedto L⁵⁵; and

L⁵⁵ represents a single bond or a C1-C8 alkanediyl group where amethylene group can be replaced by an oxygen atom or carbonyl group. Thealicyclic hydrocarbon group represented by R⁵² may be monocyclic orpolycyclic one. Examples of the alicyclic hydrocarbon group include amonocyclic hydrocarbon group such as a C3-C18 cycloalkyl group (e.g. acyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexylgroup) and a polycyclic alicyclic hydrocarbon group such as an adamantylgroup, or a norbornyl group.

Examples of the alicyclic hydrocarbon group having a substituent includea 3-hydroxyadamantyl group, and a 3-methyladamantyl group. Examples ofthe C1-C8 aliphatic hydrocarbon group include an alkyl group such asmethyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl,n-pentyl, n-hexyl, n-heptyl, 2-ethylhexyl and n-octyl groups.

Examples of the alicyclic hydrocarbon group having a substituent for R⁵²include 3-methyladamantyl group.

R⁵² is preferably an unsubstituted C3-C18 alicyclic hydrocarbon group,and more preferably an adamantyl, norbornyl or cyclohexyl group.

Examples of the divalent saturated hydrocarbon group for L⁵⁵ include adivalent saturated aliphatic hydrocarbon group and a divalent saturatedalicyclic hydrocarbon group, and a divalent saturated aliphatichydrocarbon group is preferred.

Examples of the divalent saturated aliphatic hydrocarbon group includean alkanediyl group such as methylene, ethylene, propanediyl, butanediyland pentanediyl groups.

Examples of the divalent saturated alicyclic hydrocarbon group includeany of a monocyclic group and a polycyclic group. Examples of themonocyclic group include cycloalkanediyl group such as cyclopentanediyland cyclohexanediyl groups. Examples of the polycyclic group includeadamantanediyl and norbornanediyl groups. Examples of the saturatedhydrocarbon group in which a methylene group has been replaced by anoxygen atom or a carbonyl group include groups represented by formula(L1-1) to formula (L1-4). In formula (L1-1) to formula (L1-4), *represents a binding site to an oxygen atom.

In the formulae, X^(X1) represents an oxycarbonyl group or a carbonyloxygroup,

L^(X1) represents a C1-C16 divalent saturated aliphatic hydrocarbongroup,

L^(X2) represents a single bond or a C1-C15 divalent saturated aliphatichydrocarbon group,

provided that the total number of the carbon atoms contained in thegroups of L^(X1) and L^(X2) is 16 or less;

L^(X3) represents a single bond or a C1-C17 divalent saturated aliphatichydrocarbon group,

L^(X4) represents a single bond or a C1-C16 divalent saturated aliphatichydrocarbon group,

provided that the total number of the carbon atoms contained in thegroups of L^(X3) and L^(X4) is 17 or less;

L^(X5) represents a C1-C15 divalent saturated aliphatic hydrocarbongroup,

L^(X6) and L^(X7) each independently represent a single bond or a C1-C14divalent saturated aliphatic hydrocarbon group,

provided that the total number of the carbon atoms contained in thegroups of L^(X5), L^(X6) and L^(X7) is 15 or less;

L^(X8) and L^(X9) each independently represent a single bond or a C1-C12divalent saturated aliphatic hydrocarbon group,

W^(X1) represents a C3-C15 divalent saturated alicyclic hydrocarbongroup,

provided that the total number of the carbon atoms contained in thegroups of L^(X8), L^(X9) and W^(X1) is 15 or less.

L^(X1) is preferably a C1-C8 divalent saturated aliphatic hydrocarbongroup, and more preferably a methylene group or an ethylene group.

L^(X2) is preferably a single bond or a C1-C8 divalent saturatedaliphatic hydrocarbon group, and more preferably a single bond.

L^(X3) is preferably a C1-C8 divalent saturated aliphatic hydrocarbongroup.

L^(X4) is preferably a single bond or a C1-C8 divalent saturatedaliphatic hydrocarbon group.

L^(X5) is preferably a C1-C8 divalent saturated aliphatic hydrocarbongroup, and more preferably a methylene group or an ethylene group.

L^(X6) is preferably a single bond or a C1-C8 divalent saturatedaliphatic hydrocarbon group, and more preferably a methylene group or anethylene group.

L^(X7) is preferably a single bond or a C1-C8 divalent saturatedaliphatic hydrocarbon group.

L^(X8) is preferably a single bond or a C1-C8 divalent saturatedaliphatic hydrocarbon group, and more preferably a single bond or amethylene group.

L^(X9) is preferably a single bond or a C1-C8 divalent saturatedaliphatic hydrocarbon group, and more preferably a single bond or amethylene group.

W^(X1) is preferably a C3-C10 divalent saturated alicyclic hydrocarbongroup, and more preferably a cyclohexanediyl group and an adamantanediylgroup.

Examples of the group represented by the formula (L1-1) include thefollowing ones.

Examples of the group represented by the formula (L1-2) include thefollowing ones.

Examples of the group represented by the formula (L1-3) include thefollowing ones.

Examples of the group represented by the formula (L1-4) include thefollowing ones.

L⁵⁵ is preferably a single bond, a methylene group, and ethylene groupor the group represented by the formula (L1-1), more preferably a singlebond or the group represented by the formula (L1-1).

Examples of the structural unit represented by formula (a5-1) includethe following ones and those represented by following formulae in whicha methyl group has been replaced by a hydrogen atom.

When the resin (A) further has the structural unit represented byformula (a5), the content thereof is preferably 1 to 30% by mole, morepreferably 2 to 20% by mole, and still more preferably 3 to 15% by mole,based on all the structural units of the resin.

The resin (A) can further have any other structural unit known in thephotoresist field.

The resin (A) is preferably a resin which comprises the structural unit(a1), more preferably a resin which comprises the structural unit (a1)and the structural unit (s).

The resin (A) has, as the structural unit (a1), preferably at least one,more preferably two or more structural units selected from thestructural unit (a1-1), the structural unit (a1-2).

The resin (A) has, as the structural unit (s), preferably at least onestructural unit selected from the structural unit (a2) and thestructural unit (a3). For the resin (A), the structural unit (a2) ispreferably the structural unit represented by formula (a2-1). For theresin (A), the structural unit (a2) is preferably at least onestructural unit selected from the group consisting of the structuralunits represented by formulae (a3-1-1), (a3-1-2), (a3-1-3), (a3-1-4),(a3-2-1), (a3-2-2), (a3-2-3), (a3-2-4), (a3-4-1) and (a3-4-2).

The resin (A) can be produced by polymerizing a monomer as mentionedabove in a manner of radical polymerization or a known polymerizationmethod.

The weight-average molecular weight of the resin (A) is usually 2,000 ormore, preferably 2,500 or more, and more preferably 3,000 or more, andusually 50,000 or less, preferably 30,000 or less, more preferably15,000 or less.

The weight-average molecular weight can be measured with gel permeationchromatography (standard: polyethylene). The detailed method ofmeasurement is described in Examples of the present specification.

Examples of another resin than Resin (A) include what consists of astructural unit having no acid-labile group, preferably what has thestructural unit having a halogen atom such as the structural unit (a4).Here, such another resin is referred to as “Resin (X)”. Resin (X) may beone which consists of the structural unit having a fluorine atom, or onewhich further comprise the structural unit (a2), the structural unit(a3), the structural unit (a5) or another structural unit having noacid-labile group, known in the art. Resin (X) preferably contains thestructural unit having a fluorine atom and the structural unit (a5).

In Resin (X), the content of the structural unit (a4) is preferably 40%by mole or more, more preferably 45% by mole or more, still morepreferably 50% by mole or more based on sum of the structural units inthe resin.

Resin (X) usually has 8000 or more of the weight-average molecularweight, preferably 10000 or more of the weight-average molecular weight.The resin usually has 80,000 or less of the weight-average molecularweight, preferably has 60,000 or less of the weight-average molecularweight.

The weight-average molecular weight can be measured with known methodssuch as liquid chromatography or gas chromatography.

The resin (X) can be obtained by conducting polymerization reaction ofthe corresponding monomer or monomers. The polymerization reaction isusually carried out in the presence of a radical initiator. Thispolymerization reaction can be conducted according to known methods.

When the photoresist composition contains Resin (X), the content of theresin is preferably 1 to 60 weight parts, more preferably 1 to 50 weightparts, and still more preferably 1 to 40 weight parts, and further stillmore preferably 2 to 30 weight parts, relative to 100 parts of Resin(A).

The total content of the resins in the photoresist composition of thepresent invention is usually 80% by mass or more, preferably 90% by massor more, based on sum of solid component, and usually 99% by mass orless based on sum of solid component.

In this specification, “solid component” means components other thansolvent in the photoresist composition.

<Acid generator (B)>

The photoresist composition of the disclosure may further contain aknown acid generator which is sometimes referred to as “acid generator(B)”.

The acid generator (B) may be a nonionic acid generator or an ionic acidgenerator. Examples of the nonionic acid generator include anorgano-halogen compound, a sulfonate compound such as a2-nitrobenzylsulfonate, an aromatic sulfonate, an oxime sulfonate, anN-sulfonyloxyimide, a sulfonyloxyketone and diazonaphthoquinone4-sulfonate, and a sulfone compound such as a disulfone, a ketosulfoneand a sulfonyldiazomethane. Examples of the ionic acid generator includean onium salt compound such as a diazonium salt, a phosphonium salt, asulfonium salt and an iodonium salt. Examples of the anion of the oniumsalt include a sulfonic acid anion, a sulfonylimide anion and asulfonylmethide anion.

Specific examples of the acid generator (B) include acid generatorsdescribed in JP 63-26653 A, JP 55-164824 A, JP62-69263 A, JP63-146038A,JP63-163452A, JP62-153853A, JP63-146029A, U.S. Pat. No. 3,779,778, U.S.Pat. No. 3,849,137, DE Patent No. 3914407 and EP Patent No. 126,712.Other examples of that include acid generators described inJP2013-68914A, JP2013-3155A and JP2013-11905A.

The acid generator for the photoresist composition is preferably afluorine-containing acid generator, and more preferably afluorine-containing organic sulfonate acid generator.

Preferable examples of the acid generator include a salt represented bythe formula (B1):

wherein Q¹¹ and Q¹² each independently represent a fluorine atom or aC1-C6 perfluoroalkyl group,

L^(B1) represents a single bond or a C1-C24 divalent saturatedhydrocarbon group in which a methylene group can be replaced by —O— or—CO— and in which a hydrogen atom can be replaced by a fluorine atom ora hydroxy group, and

Y represents a methyl group which can have a substituent or a C3-C18monovalent alicyclic hydrocarbon group which can have a substituent andin which a methylene group can be replaced by —O—, —CO— or —SO₂—, andZ1⁺ represents an organic cation.

For Q¹¹ and Q¹², examples of the perfluoroalkyl group include examplesof those for Q¹ and Q², and a trifluoromethyl group is preferred. Q¹¹and Q¹² each independently preferably represent a fluorine atom or atrifluoromethyl group, and Q¹¹ and Q¹² are more preferably fluorineatoms.

Examples of the divalent saturated hydrocarbon group represented by Linclude linear alkanediyl groups, branched chain alkanediyl groups, amonocyclic divalent alicyclic hydrocarbon group, a polycyclic divalentalicyclic hydrocarbon group and combinations of them. Specific examplesof them include linear alkanediyl groups such as a methylene group, anethylene group, a propane-1,3-diyl group, a butane-1,4-diyl group, apentane-1,5-diyl group, a hexane-1,6-diyl group, a heptane-1,7-diylgroup, an octane-1,8-diyl group, a nonane-1,9-diyl group, adecane-1,10-diyl group, a undecane-1,11-diyl group, a dodecane-1,12-diylgroup, a tridecane-1,13-diyl group, a tetradecane-1,14-diyl group, apentadecane-1,15-diyl group, a hexadecane-1,16-diyl group andheptadecane-1,17-diyl group; branched chain alkanediyl groups such as anethane-1,1-diyl group, a propane-1,1-diyl group, a propane-1,2-diylgroup, a propane-2,2-diyl group, a pentane-2,4-diyl group, a2-methylpropane-1,3-diyl group, a 2-methylpropane-1,2-diyl group, apentane-1,4-diyl group and 2-methylbutane-1,4-diyl group; a monocyclicdivalent alicyclic hydrocarbon group such as a cyclobutan-1,3-diylgroup, cyclopentane-1,3-diyl group, a cyclohexane-1,4-diyl group, and acyclooctane-1,5-diyl group; and a polycyclic divalent alicyclichydrocarbon group such as a norbornane-1,4-diyl group, anorbornane-2,5-diyl group, an adamantane-1,5-diyl group and anadamantane-2,6-diyl group.

When L^(B1) represents a divalent saturated hydrocarbon group in which amethylene group has been replaced by an oxygen atom or a carbonyl group,examples of L^(B1) include the moiety represented by any one of formulae(b1-1) to (b1-3) as follow;

wherein L^(b2) represents a single bond or a C1 to C22 divalentsaturated hydrocarbon group in which a hydrogen atom can be replaced bya fluorine atom, and

L^(b3) represents a single bond or a C1 to C22 divalent saturatedhydrocarbon group in which a hydrogen atom can be replaced by a fluorineatom or a hydroxyl group and in which a methylene group can be replacedby an oxygen atom or a carbonyl group, provided that the total number ofthe carbon atoms in L^(b2) and L^(b3) is up to 22;

L^(b4) represents a single bond or a C1 to C22 divalent saturatedhydrocarbon group in which a hydrogen atom can be replaced by a fluorineatom, and L^(b5) represents a single bond or a C1 to C22 divalentsaturated hydrocarbon group in which a hydrogen atom can be replaced bya fluorine atom or a hydroxyl group and in which a methylene group canbe replaced by an oxygen atom or a carbonyl group, provided that thetotal number of the carbon atoms in L^(b4) and L^(b5) is up to 22;

L^(b6) represents a C1 to C23 divalent saturated hydrocarbon group inwhich a hydrogen atom can be replaced by a fluorine atom or a hydroxylgroup, and L^(b7) represents a single bond or a C1 to C23 divalentsaturated hydrocarbon group in which a hydrogen atom can be replaced bya fluorine atom or a hydroxyl group and in which a methylene group canbe replaced by an oxygen atom or a carbonyl group, provided that thetotal number of the carbon atoms in L^(b6) and L^(b7) is up to 23; and *represents a binding site to Y.

In formula (b1-1) to formula (b1-3), when a methylene group has beenreplaced by an oxygen atom or a carbonyl group, the carbon number of thesaturated hydrocarbon group corresponds to the number of the carbon atombefore replacement.

Examples of the divalent saturated hydrocarbon group are the sameexamples as the divalent saturated hydrocarbon group of L^(b1).

L^(b2) is preferably a single bond.

L^(b3) is preferably a C1 to C4 divalent saturated hydrocarbon group.

L^(b4) is preferably a C1 to C8 divalent saturated hydrocarbon groupwhere a hydrogen atom can be replaced by a fluorine atom.

L^(b5) is preferably a single bond or a C1 to C8 divalent saturatedhydrocarbon group.

L^(b6) is preferably a single bond or a C1 to C4 divalent saturatedhydrocarbon group where a hydrogen atom can be replaced by a fluorineatom.

L^(b7) is preferably a single bond or a C1 to C18 divalent saturatedhydrocarbon group where a hydrogen atom can be replaced by a fluorineatom or a hydroxy group, and where a methylene group can be replaced byan oxygen atom or a carbonyl group.

Among these, the group represented by the formula (b1-1) or the formula(b1-3) is preferred.

Examples of the divalent group represented by the formula (b1-1) includethe following groups represented by formula (b1-4) to formula (b1-8):

wherein L^(b8) represents a single bond or a C1 to C22 divalentsaturated hydrocarbon group where a hydrogen atom can be replaced by afluorine atom or a hydroxy group;

L^(b9) represents a C1 to C20 divalent saturated hydrocarbon group, andL^(b1) represents a single bond or a C1 to C19 divalent saturatedhydrocarbon group where a hydrogen atom can be replaced by a fluorineatom or a hydroxy group, provided that the total number of carbon atomscontained in the group of L^(b9) and L^(b10) is 20 or less;

L^(b11) represents a C1 to C21 divalent saturated hydrocarbon group, andL^(b12) represents a single bond or a C1 to C20 divalent saturatedhydrocarbon group where a hydrogen atom can be replaced by a fluorineatom or a hydroxy group, provided that the total number of carbon atomscontained in the group of L^(b11) and L^(b12) is 21 or less;

L^(b13) represents a C1 to C19 divalent saturated hydrocarbon group,L^(b14) represents a single bond or a C1 to C18 divalent saturatedhydrocarbon group, and L^(b15) represents a single bond or a C1 to C18divalent saturated hydrocarbon group where a hydrogen atom can bereplaced by a fluorine atom or a hydroxy group, provided that the totalnumber of carbon atoms contained in the group of L^(b13), L^(b14) andL^(b5) is 19 or less;

L^(b16) represents a C1 to C18 divalent saturated hydrocarbon group,L^(b17) represents a C1 to C18 divalent saturated hydrocarbon group, andL^(b18) represents a single bond or a C1 to C17 divalent saturatedhydrocarbon group where a hydrogen atom can be replaced by a fluorineatom or a hydroxy group, provided that the total number of carbon atomscontained in the group of L^(b16), L^(b17) and L^(b18) is 19 or less;and * represents a binding site to Y.

L^(b8) is preferably a C1 to C4 divalent saturated hydrocarbon group.

L^(b9) is preferably a C1 to C8 divalent saturated hydrocarbon group.

L^(b10) is preferably a single bond or a C1 to C19 divalent saturatedhydrocarbon group, and more preferably a single bond or a C1 to C8divalent saturated hydrocarbon group.

L^(b11) is preferably a C1 to C8 divalent saturated hydrocarbon group.

L^(b12) is preferably a single bond or a C1 to C8 divalent saturatedhydrocarbon group.

L^(b13) is preferably a C1 to C12 divalent saturated hydrocarbon group.

L^(b14) is preferably a single bond or a C1 to C6 divalent saturatedhydrocarbon group.

L^(b15) is preferably a single bond or a C1 to C18 divalent saturatedhydrocarbon group, and more preferably a single bond or a C1 to C8divalent saturated hydrocarbon group.

L^(b16) is preferably a C1 to C12 divalent saturated hydrocarbon group.

L^(b17) is preferably a C1 to C6 divalent saturated hydrocarbon group.

L^(b18) is preferably a single bond or a C1 to C17 divalent saturatedhydrocarbon group, and more preferably a single bond or a C1 to C4divalent saturated hydrocarbon group.

Examples of the divalent group represented by the formula (b1-3) includethe following groups represented by formula (b1-9) to formula (b1-11):

wherein L^(b19) represents a single bond or a C1 to C23 divalentsaturated hydrocarbon group where a hydrogen atom can be replaced by afluorine atom, and L^(b20) represent a single bond or a C1 to C23divalent saturated hydrocarbon group where a hydrogen atom can bereplaced by a fluorine atom, a hydroxy group or an acyloxy group, and amethylene group contained in an acyloxy group can be replaced by anoxygen atom or a carbonyl group, and a hydrogen atom contained in anacyloxy group can be replaced by a hydroxy group, provided that thetotal number of carbon atoms contained in the group of L^(b19) andL^(b20) is 23 or less;

L^(b21) represents a single bond or a C1 to C21 divalent saturatedhydrocarbon group where a hydrogen atom can be replaced by a fluorineatom, L^(b22) represents a single bond or a C1 to C21 divalent saturatedhydrocarbon group, and L^(b23) represents a single bond or a C1 to C21divalent saturated hydrocarbon group where a hydrogen atom can bereplaced by a fluorine atom, a hydroxy group or an acyloxy group, and amethylene group contained in an acyloxy group can be replaced by anoxygen atom or a carbonyl group, and a hydrogen atom contained in anacyloxy group can be replaced by a hydroxy group, provided that thetotal number of carbon atoms contained in the group of L^(b21), L^(b22)and L^(b23) is 21 or less;

L^(b24) represents a single bond or a C1 to C20 divalent saturatedhydrocarbon group where a hydrogen atom can be replaced by a fluorineatom, L^(b25) represents a single bond or a C1 to C21 divalent saturatedhydrocarbon group, and L^(b26) represents a single bond or a C1 to C20divalent saturated hydrocarbon group where a hydrogen atom can bereplaced by a fluorine atom, a hydroxy group or an acyloxy group, and amethylene group contained in an acyloxy group can be replaced by anoxygen atom or a carbonyl group, and a hydrogen atom contained in anacyloxy group can be replaced by a hydroxy group, provided that thetotal number of carbon atoms contained in the group of L^(b24), L^(b25)and L^(b26) is 21 or less;

and * represents a binding site to Y.

In formula (b1-9) to formula (b1-11), when a hydrogen atom has beenreplaced by an acyloxy group, the carbon number of the saturatedhydrocarbon group corresponds to the number of the carbon atom, CO and Oin addition to the carbon number of the saturated hydrocarbon group.

L^(B1) is preferably one represented by formulae (b1-1), (b1-2) or(b1-3), more preferably *²—CO—O—(CH₂)_(t1)— or *²—(CH₂)_(t2)—O—CO— wheret1 represents an integer of 0 to 6, t2 represents an integer of 2 to 6,and *² represents a binding position to —C(Q¹¹)(Q¹²)-.

The monovalent alicyclic hydrocarbon group for Y may be a monocyclic oneor polycyclic one such as a spiro ring.

Preferred examples of the alicyclic hydrocarbon group represented by Yinclude those represented by the formulae (Y1) to (Y38).

Among the groups represented by the formulae (Y1) to (Y38), preferredare those represented by formulae (Y1) to (Y20), (Y30) and (Y31); morepreferred are those represented by the formulae (Y11), (Y15), (Y16),(Y19), (Y30) and (Y31); and still more preferred are those representedby the formulae (Y11), (Y15) and (Y30).

Substituents on the alicyclic hydrocarbon groups for Y include a halogenatom, a C1-C12 alkyl group, a C1-C12 hydroxy-containing alkyl group, ahydroxyl group, a C1-C12 alkoxy group, a C3-C16 alicyclic hydrocarbongroup, a C6-C18 aromatic hydrocarbon group, a C7-C21 aralkyl group, aC2-C4 acyl group, a glycidyloxy group, and —(CH₂)_(j2)—O—CO—R^(b1′)— inwhich R^(b1′) is a C1-C16 alkyl group and j2 is an integer of 0 to 4.

Examples of hydroxyl-containing alkyl group include a hydroxymethylgroup and a hydroxyethyl group.

Examples of the C1-C12 alkoxy group include a methoxy group, an ethoxygroup, a propoxy group, a butoxy group, a pentyloxy group, a hexyloxygroup, a heptyloxy group, an octyloxy group, a decyloxy group and adodecyloxy group.

Examples of the aromatic hydrocarbon group include an aryl group such asa phenyl group, a naphthyl group, an anthryl group, a p-methylphenylgroup, a p-tert-butylphenyl group, a p-adamantylphenyl group, a tolylgroup, a xylyl group, a cumyl group, a mesityl group, a biphenyl group,a phenanthryl group, a 2,6-diethylphenyl group and a2-methyl-6-ethylphenyl group. Examples of the aralkyl group include abenzyl group, phenylpropyl group, a phenethyl group, a naphthylmethylgroup, or a naphthylethyl group.

Examples of the acyl group include an acetyl group, a propyonyl groupand a butyryl group.

Examples of the halogen atom include a fluorine atom, a chlorine atom, abromine atom and an iodine atom.

Examples of Y include the groups as follow.

where * represents a binding position.

Y represents preferably a C3-C18 alicyclic hydrocarbon group which mayhave a substituent, more preferably an amadantyl group which may have asubstituent, and still more preferably an amadantyl group, ahydroxyamadantyl group, an oxoamadantyl group, or the following group.

Preferred examples of the sulfonic acid anion of the salt represented byformula (B1) include salts represented by the formulae (B1-A-1) to(B1-A-55), preferably the formulae (B1-A-1) to (B1-A-4), (B1-A-9),(B1-A-10), (B1-A-24) to (B1-A-33), (B1-A-36) to (B1-A-40) and (B1-A-47)to (B1-A-55).

In these formulae, the symbols Q¹¹, Q¹² and Y are defined as above,R^(i2), R^(i3), R^(i4), R^(i5), R^(i6) and R^(i7) each independentlyrepresent a C1-C4 alkyl group, preferably a methyl group or an ethylgroup, R^(i8) represents a C1-C12 saturated hydrocarbon group[preferably a C1-C4 alkyl group], a C5-C12 monovalent alicyclichydrocarbon group, or a combined group of them, preferably a methylgroup, an ethyl group, a cyclohexyl group or an adamantyl group, and L⁴⁴represents a single bond or a C1-C4 alkanediyl group.

Specific examples of the anion for the salt represented by formula (B1)include the following anions.

Among them, preferred are those represented by formulae (B1a-1) to(B1a-3), (B1a-7) to (B1a-16), (B1a-18), (B1a-19) and (B1a-22) to(B1a-34).

Examples of the organic counter ion represented by Z1⁺ include an oniumcations as referred to Z⁺ of formula (I), for example those representedby the formulae (b2-1), (b2-2), (b2-3) and (b2-4), and a sulfoniumcation and an iodonium cation are preferred, and a sulfonium cation,specifically an arylsulfonium cation, is more preferred.

Specific examples of the acid generator include the following saltsrepresented by formulae (B1-1) to (B1-48). Among them, those whichcomprise an arylsulfonium cation are preferred, the salts represented byformulae (B1-1), (B1-2), (B1-3), (B1-5), (B1-6), (B1-7), (B1-11),(B1-12), (B1-13), (B1-14), (B1-17), (B1-20), (B1-21), (B1-22), (B1-23),(B1-24), (B1-25), (B1-26), (B1-29) and (B1-31) to (B1-48) are morepreferred.

The content of the acid generator (B) is preferably 1 to 40 parts bymass, more preferably 3 to 35 parts by mass, still more preferably 30parts by mass, further more preferably 25 parts by mass, per 100 partsof Resin (A).

When the photoresist composition further contains the acid generator(B), the total content of the acid generator (B) and the saltrepresented by formula (I) is preferably 1.5 to 40 parts by mass, morepreferably 3 to 35 parts by mass, per 100 parts of Resin (A). When thephotoresist contains the acid generator (B), the weight ratio of thesalt and the acid generator (B) is usually 1:99 to 99:1, preferably 2:98to 98:2, more preferably 5:95 to 95:5.

<Solvent>

Preferably, the photoresist composition of the disclosure furthercontains a solvent.

The amount of the solvent is usually 90% by weight or more, preferably92% by weight or more preferably 94% by weight or more based on totalamount of the photoresist composition of the present invention. Theamount of the solvent is usually 99.9% by weight or less and preferably99% by weight or less based on total amount of the photoresistcomposition of the present invention. The content can be measured withknown methods such as liquid chromatography or gas chromatography.

Examples of the solvent include a glycol ether ester such as ethylcellosolve acetate, methyl cellosolve acetate and propylene glycolmonomethyl ether acetate; a glycol ether such as propylene glycolmonomethyl ether; an ester such as ethyl lactate, butyl acetate, amylacetate and ethyl pyruvate; a ketone such as acetone, methyl isobutylketone, 2-heptanone and cyclohexanone; and a cyclic ester such asγ-butyrolactone.

<Quencher>

The photoresist composition of the disclosure may further contain aquencher such as a basic compound. The “quencher” has the property thatit can trap an acid, especially an acid generated from the acidgenerator by exposure to light for lithography.

Examples of the quencher include a basic compound, such as a basicnitrogen-containing organic compound, and a salt which generates an acidhaving acidity weaker than an acid generated from the acid generators.

Examples of the basic nitrogen-containing organic compound include anamine compound such as an aliphatic amine, an aromatic amine and anammonium salt. Examples of the aliphatic amine include a primary amine,a secondary amine and a tertiary amine. Examples of the aromatic amineinclude an aromatic amine.

Examples of the quencher include 1-naphthylamine, 2-naphthylamine,aniline, diisopropylaniline, 2-, 3- or 4-methylaniline, 4-nitroaniline,N-methylaniline, N,N-dimethylaniline, diphenylamine, hexylamine,heptylamine, octylamine, nonylamine, decylamine, dibutylamine,pentylamine, dioctylamine, triethylamine, trimethylamine,tripropylamine, tributylamine, tripentylamine, trihexylamine,triheptylamine, trioctylamine, trinonylamine, tridecylamine,methyldibutylamine, methyldipentylamine, methyldihexylamine,methyldicyclohexylamine, methyldiheptylamine, methyldioctylamine,methyldinonylamine, methyldidecylamine, ethyldibutylamine,ethyldipentylamine, ethyldihexylamine, ethyldiheptylamine,ethyldioctylamine, ethyldinonylamine, ethyldidecylamine,dicyclohexylmethylamine, tris [2-(2-methoxyethoxy)ethyl]amine,triisopropanolamine, ethylenediamine, tetramethylenediamine,hexamethylenediamine, 4,4′-diamino-1,2-diphenylethane,4,4′-diamino-3,3′-dimethyldiphenylmethane,4,4′-diamino-3,3′-diethyldiphenyl methane, piperazine, morpholine,piperidine, hindered amine compound having a piperidine structure,2,2′-methylenebisaniline, imidazole, 4-methylimidazole, pyridine,4-methylpyridine, 1,2-di(2-pyridyl)ethane, 1,2-di(4-pyridyl)ethane,1,2-di(2-pyridyl)ethene, 1,2-di(4-pyridyl)ethene, 1,3-di(4-pyridyl)propane, 1, 2-di(4-pyridyloxy) ethane, di(2-pyridyl) ketone,4,4′-dipyridyl sulfide, 4,4′-dipyridyl disulfide, 2,2′-dipyridylamine,2,2′-dipicolylamine and bipyridine.

Examples of the quaternary ammonium hydroxide includetetramethylammonium hydroxide, tetrabutylammonium hydroxide,tetrahexylammonium hydroxide, tetraoctylammonium hydroxide,phenyltrimethylammonium hydroxide,(3-trifluoromethylphenyl)trimethylammonium hydroxide and(2-hydroxyethyl)trimethylammonium hydroxide (so-called “choline”).

As to salt which generates an acid having acidity weaker than an acidgenerated from the acid generators, the acidity in the salts is shown bythe acid dissociation constant (pKa).

The acid dissociation constant of acid generated from the salt for aquencher is usually −3<pKa.

The salt for a quencher is preferably a salt of −1<pKa<7, and morepreferably a salt of 0<pKa<5.

Specific examples of the salt for a quencher include the following ones,an onium carboxylic acid salt such as the salt of formula (D), and saltsrecited in US2012/328986A1, US2011/171576A1, US2011/201823A1,JP2011-39502A1, and US2011/200935A1.

The photoresist composition comprises preferably onium carboxylic acidsalt, more preferably the salt of formula (D).

The content of quencher is preferably 0.01 to 5% by mass, morepreferably 0.01 to 4% by mass, still more preferably 0.01 to 3% by mass,based on sum of solid component.

The photoresist compositions of the present invention may comprise, ifnecessary, a small amount of various additives such as a sensitizer, adissolution inhibitor, other polymers, a surfactant, a stabilizer and adye as long as the effect of the present invention is not prevented.

The photoresist compositions of the present invention can be prepared bymixing, usually in a solvent, an acid generator which contains the saltrepresented by formula (I) and Resin (A), and if necessary a quencher,and/or additives at a suitable ratio for the composition, optionallyfollowed by filtrating the mixture with a filter having 0.003 μm to 0.2μm of a pore size.

The order of mixing these components is not limited to any specificorder. The temperature at mixing the components is usually 10 to 40° C.,which can be selected in view of the resin or the like.

The mixing time is usually 0.5 to 24 hours, which can be selected inview of the temperature. The means for mixing the components is notlimited to specific one. The components can be mixed by being stirred.

The amounts of the components in the photoresist compositions can beadjusted by selecting the amount to be used for production of them.

The photoresist compositions of the disclosure are useful for achemically amplified photoresist composition.

A photoresist pattern can be produced by the following steps (1) to (5):

(1) a step of applying the photoresist composition of the presentinvention on a substrate,

(2) a step of forming a composition film by conducting drying,

(3) a step of exposing the composition film to radiation,

(4) a step of baking the exposed composition film, and

(5) a step of developing the baked composition film with an alkalinedeveloper.

The applying of the photoresist composition on a substrate is usuallyconducted using a conventional apparatus such as spin coater. Examplesof the substrate include a silicon wafer or a quartz wafer on which asensor, a circuit, a transistor or the like is formed.

The formation of the composition film is usually conducted using aheating apparatus such as hot plate or a decompressor, and the heatingtemperature is usually 50 to 200° C. When the pressure is reduced duringheating, the operation pressure is usually 1 to 1.0×10⁵ Pa. The heatingtime is usually 10 to 180 seconds.

The composition film obtained is exposed to radiation using an exposuresystem. The exposure is usually conducted through a mask having apattern corresponding to the desired photoresist pattern. Examples ofthe exposure source include a light source radiating laser light in aUV-region such as a KrF excimer laser (wavelength: 248 nm), an ArFexcimer laser (wavelength: 193 nm) and a F₂ laser (wavelength: 157 nm),a light source radiating harmonic laser light in a far UV region or avacuum UV region by wavelength conversion of laser light from a solidlaser light source (such as YAG or semiconductor laser), and a lightsource radiating electron beam or EUV (extreme ultraviolet) light.

The temperature of baking of the exposed composition film is usually 50to 200° C., and preferably 70 to 150° C.

The development of the baked composition film is usually carried outusing a development apparatus. The development method includes dippingmethods, paddle methods, spray methods and dynamic dispense method. Thedeveloping temperature is preferably 5 to 60° C., and the developingtime is preferably 5 to 300 seconds.

The positive and negative type photoresist patterns can be obtained bythe development depending on a developer to be used therefor.

When a positive type photoresist pattern is prepared from thephotoresist composition of the present invention, the development can beconducted with an alkaline developer. The alkaline developer to be usedmay be any one of various alkaline aqueous solution used in the art.Generally, an aqueous solution of tetramethylammonium hydroxide or(2-hydroxyethyl)trimethylammonium hydroxide (commonly known as“choline”) is often used. The alkaline developer may comprise asurfactant.

After development, the photoresist film having photoresist pattern ispreferably washed with ultrapure water, and the remained water on thephotoresist film and the substrate is preferably removed therefrom.

When a negative type photoresist pattern is prepared from thephotoresist composition of the present invention, the development can beconducted with a developer containing an organic solvent, such developeris sometimes referred to as “organic developer”.

Examples of an organic solvent for organic developer include ketonesolvents such as 2-hexanone, 2-heptanone; glycolether ester solventssuch as propyleneglycolmonomethylether acetate; ester solvents such asbutyl acetate; glycolether solvents such aspropyleneglycolmonomethylether; amide solvents such asN,N-dimethylacetamide; and aromatic hydrocarbon solvents such asanisole.

The content of organic solvent is preferably from 90% to 100% by weight,more preferably from 95% to 100% by weight, in an organic developer.Preferred is that the organic developer essentially consists of anorganic solvent.

Among them, the organic developer is preferably a developer comprisingbutyl acetate and/or 2-heptanone.

The total content of butyl acetate and 2-heptanone is preferably from90% to 100% by weight, more preferably from 95% to 100% by weight.Preferred is that the organic developer essentially consists of butylacetate and/or 2-heptanone.

The organic developer may comprise a surfactant or a very small amountof water.

Development with an organic developer can be stopped by replacing thedeveloper by other solvent than it such as alcohol.

The photoresist composition of the present invention is suitable for KrFexcimer laser lithography, ArF excimer laser lithography, EUV (extremeultraviolet) lithography, EUV immersion lithography and EB (electronbeam) lithography.

EXAMPLES

The present invention will be described more specifically by Examples,which are not construed to limit the scope of the present invention.

The “%” and “part(s)” used to represent the content of any component andthe amount of any material used in the following examples andcomparative examples are on a weight basis unless otherwise specificallynoted.

The weight-average molecular weight of any material used in thefollowing examples is a value found by gel permeation chromatographyunder the following conditions.

Column: HLC-8120GPC Type (Three Columns with guard column), TSKgelMultipore HXL-M, manufactured by TOSOH CORPORATION

Solvent: Tetrahydrofuran, Flow rate: 1.0 mL/min.

Detector: RI detector

Column temperature: 40° C.

Injection volume: 100 μL

Standard reference material: Standard polystyrene

Structures of compounds were determined by mass spectrometry (LiquidChromatography: 1100 Type, manufactured by AGILENT TECHNOLOGIES LTD.,Mass Spectrometry: LC/MSD Type, manufactured by AGILENT TECHNOLOGIESLTD.). Hereinafter the peak value in the molecular ion spectrumdetermined by the spectrometry is referred to as “MASS”.

Example 1

In a reactor, 50.3 parts of the salt represented by the formula (I-1-a)and 250 parts of acetonitrile were mixed and stirred at 40° C. for onehour. To resultant mixture, 23.8 parts of the salt represented by theformula (I-1-b) was added over 10 minutes, and then its temperature wasincreased to 70° C. Then the obtained mixture was stirred at 70° C. for2 hours to obtain a solution which contained a salt represented byformula (I-1-c).

The solution was cooled to 23° C., and thereto was added a mixture of 13parts of a salt represented by formula (I-1-d) and 13 parts ofacetonitrile over 90 minutes, and stirred at 23° C. for one hour,followed by being concentrated. To the concentrates, 500 parts ofchloroform and 390 parts of 5% aqueous oxalic acid solution were added,followed by being stirred at 23° C. for 30 minutes. The obtained mixturewas left so as to separate an organic layer.

To the organic layer, 250 parts of ion-exchanged water were added andstirred at 23° C. for 30 minutes for washing, followed by separating anorganic layer: The organic layer was washed four times withion-exchanged water in this manner.

Then the resultant mixture was concentrated. To the obtained residue,170 parts of tert-butylmethylether was added and the resultant mixturewas stirred, and then its supernatant was removed therefrom.

The obtained residue was dissolved in acetonitrile and then concentratedto obtain 40.3 parts of the salt represented by formula (I-1).

MS (ESI(+) Spectrum): M⁺ 263.1

MS (ESI(−) Spectrum): M⁻ 327.1

Examples 2

In a reactor, 5 parts of the salt represented by the formula (I-1-a) and25 parts of acetonitrile were mixed and stirred at 40° C. for one hour.To resultant mixture, 2.38 parts of the salt represented by the formula(I-1-b) was added at 40° C., and then its temperature was increased to60° C. Then the obtained mixture was stirred at 60° C. for 2 hours toobtain a solution which contained a salt represented by formula (I-1-c).

To the solution was added a mixture of 1.48 parts of a salt representedby formula (I-3-d) and 1.48 parts of acetonitrile, and stirred at 60° C.for 6 hours, followed by being concentrated. To the concentrates, 50parts of chloroform and 40 parts of 5% aqueous oxalic acid solution wereadded, followed by being stirred at 23° C. for 30 minutes. The obtainedmixture was left so as to separate an organic layer.

To the organic layer, 25 parts of ion-exchanged water were added andstirred at 23° C. for 30 minutes for washing, followed by separating anorganic layer: The organic layer was washed five times withion-exchanged water in this manner.

Then the resultant mixture was concentrated. To the obtained residue, 20parts of tert-butylmethylether was added and the resultant mixture wasstirred, and then its supernatant was removed therefrom. The obtainedresidue was dissolved in acetonitrile and then concentrated to obtain4.48 parts of the salt represented by formula (I-3).

MS (ESI(+) Spectrum): M⁺ 263.1

MS (ESI(−) Spectrum): M⁻ 351.1

Example 3

In a reactor, 4.84 parts of the salt represented by the formula (I-15-a)and 25 parts of acetonitrile were mixed and stirred at 40° C. for onehour. To resultant mixture, 2.38 parts of the salt represented by theformula (I-1-b) was added at 40° C., and then its temperature wasincreased to 60° C. Then the obtained mixture was stirred at 60° C. for2 hours to obtain a solution which contained a salt represented byformula (I-15-c).

To the solution was added a mixture of 1.48 parts of a salt representedby formula (I-3-d) and 1.48 parts of acetonitrile, and stirred at 60° C.for 6 hours, followed by being concentrated. To the concentrates, 50parts of chloroform and 40 parts of 5% aqueous oxalic acid solution wereadded, followed by being stirred at 23° C. for 30 minutes. The obtainedmixture was left so as to separate an organic layer.

To the organic layer, 25 parts of ion-exchanged water were added andstirred at 23° C. for 30 minutes for washing, followed by separating anorganic layer: The organic layer was washed five times withion-exchanged water in this manner.

Then the resultant mixture was concentrated. To the obtained residue, 20parts of tert-butylmethylether was added and the resultant mixture wasstirred, and then its supernatant was removed therefrom.

The obtained residue was dissolved in acetonitrile and then concentratedto obtain 4.12 parts of the salt represented by formula (I-15).

MS (ESI(+) Spectrum): M⁺ 263.1

MS (ESI(−) Spectrum): M⁻ 381.1

Example 4

In a reactor, 4.84 parts of the salt represented by the formula (I-15-a)and 25 parts of acetonitrile were mixed and stirred at 40° C. for onehour. To resultant mixture, 2.38 parts of the salt represented by theformula (I-1-b) was added at 40° C., and then its temperature wasincreased to 60° C. Then the obtained mixture was stirred at 60° C. for2 hours to obtain a solution which contained a salt represented byformula (I-15-c).

To the solution was added a mixture of 1.3 parts of a salt representedby formula (I-1-d) and 1.3 parts of acetonitrile, and stirred at 60° C.for 6 hours, followed by being concentrated. To the concentrates, 50parts of chloroform and 40 parts of 5% aqueous oxalic acid solution wereadded, followed by being stirred at 23° C. for 30 minutes. The obtainedmixture was left so as to separate an organic layer.

To the organic layer, 25 parts of ion-exchanged water were added andstirred at 23° C. for 30 minutes for washing, followed by separating anorganic layer: The organic layer was washed five times withion-exchanged water in this manner.

Then the resultant mixture was concentrated. To the obtained residue, 20parts of tert-butylmethylether was added and the resultant mixture wasstirred, and then its supernatant was removed therefrom.

The obtained residue was dissolved in acetonitrile and then concentratedto obtain 4.26 parts of the salt represented by formula (I-16).

MS (ESI(+) Spectrum): M⁺ 263.1

MS (ESI(−) Spectrum): M⁻ 357.1

Synthesis of Resin

Monomers used in the following Example are following ones.

Those monomers are sometimes referred to as “Monomer (X)” in which (X)represents the sign of the formula corresponding to the monomer. Forexample, the monomer represented by formula (a1-1-2) is referred to as“Monomer (a1-1-2)”.

Resin Synthesis Example 1

The monomers (a1-1-2), (a1-2-9), (a2-1-1) and (a3-4-2) were mixed in amolar ratio of 35/24/2.5/38.5 (monomer (a1-1-2)/monomer (a1-2-9)/monomer(a2-1-1)/monomer (a3-4-2)), and propyleneglycolmonomethyletheracetatewas added in 1.5 times parts based on total parts of all monomers toprepare a mixture. To the mixture, azobisisobutyronitrile as aninitiator in a ratio of 1 mol % based on all monomer molar amount andazobis(2,4-dimethylvaleronitrile) as an initiator in a ratio of 3 mol %based on all monomer molar amount were added, and the obtained mixturewas heated at 73° C. for about 5 hours. The reaction mixture obtainedwas poured into a large amount of a mixture of methanol and water tocause precipitation, followed by being filtrated. The collectedprecipitate was dissolved in propyleneglycolmonomethyletheracetate, andthen a large amount of the mixture of methanol and water was addedthereto to cause precipitation, followed by being filtrated: Thisreprecipitation step was conducted twice. As a result, a polymer havinga weight-average molecular weight of about 8,600 was obtained in a yieldof 78%. The polymer had the following structural units. That resin isreferred to as polymer A1.

Resin Synthesis Example 2

The monomers (a1-1-2), (a1-2-9), (a2-1-1), (a2-0-2) and (a3-4-2) weremixed in a molar ratio of 35/24/2.5/5/33.5 (monomer (a1-1-2)/monomer(a1-2-9)/monomer (a2-1-1)/monomer (a2-0-2)/monomer (a3-4-2)), andpropyleneglycolmonomethyletheracetate was added in 1.5 times parts basedon total parts of all monomers to prepare a mixture. To the mixture,azobisisobutyronitrile as an initiator in a ratio of 1 mol % based onall monomer molar amount and azobis(2,4-dimethylvaleronitrile) as aninitiator in a ratio of 3 mol % based on all monomer molar amount wereadded, and the obtained mixture was heated at 73° C. for about 5 hours.The reaction mixture obtained was poured into a large amount of amixture of methanol and water to cause precipitation, followed by beingfiltrated.

The collected precipitate was dissolved inpropyleneglycolmonomethyletheracetate, and then a large amount of themixture of methanol and water was added thereto to cause precipitation,followed by being filtrated: This reprecipitation step was conductedtwice. As a result, a polymer having a weight-average molecular weightof about 8,900 was obtained in a yield of 82%. The polymer had thefollowing structural units. That resin is referred to as polymer A2.

Resin Synthesis Example 3

The monomers (a5-1-1) and (a4-0-12) were mixed in a molar ratio of 50/50(monomer (a5-1-1)/monomer (a4-0-12)), and methylisobutylketone was addedin 1.2 times parts based on total parts of all monomers to prepare amixture. To the mixture, azobisisobutyronitrile was added as aninitiator in a ratio of 3 mol % based on all monomer molar amount, andthe obtained mixture was heated at 70° C. for about 5 hours. Thereaction mixture obtained was poured into a large amount of a mixture ofmethanol and water to cause precipitation, followed by being filtrated.As a result, a polymer having a weight-average molecular weight of about10,000 was obtained in a yield of 91%. The polymer had the followingstructural units. That resin is referred to as polymer X1.

Examples 5 to 14 and Comparative Examples 1 to 3

<Producing Photoresist Compositions>

The following components as listed in the following table were mixed anddissolved in the solvent as mentioned below, and then filtrated througha fluorine resin filter having pore diameter of 0.2 μm, to preparephotoresist compositions.

TABLE 5 Resin Acid Compound of Quencher PB (kind/ generator formula (I)(kind/ (° C.)/ Comp. amount (kind/amount (kind/amount amount PEB No.(part)) (part)) (part)) (part)) (° C.) 1 X1/0.4 None I-1/0.90 D1/0.28120/110 A1/10 2 X1/0.4 B1-21/0.30 I-1/0.40 D1/0.28 120/110 A1/10B1-22/0.20 3 X1/0.4 B1-21/0.60 I-1/0.20 D1/0.28 120/110 A1/10 B1-22/0.404 X1/0.4 B1-21/0.30 I-1/0.40 D1/0.28 120/110 A2/10 B1-22/0.20 5 X1/0.4None I-3/0.90 D1/0.28 120/110 A1/10 6 X1/0.4 B1-21/0.30 I-3/0.40 D1/0.28120/110 A2/10 B1-22/0.20 7 X1/0.4 None I-15/0.9 D1/0.28 120/110 A1/10 8X1/0.4 B1-21/0.30 I-15/0.4 D1/0.28 120/110 A2/10 B1-22/0.20 9 X1/0.4None I-16/0.9 D1/0.28 120/110 A1/10 10 X1/0.4 B1-21/0.30 I-16/0.4D1/0.28 120/110 A2/10 B1-22/0.20 Compar. X1/0.4 None I-X1/0.9 D1/0.28120/110 comp 1 A1/10 Compar. X1/0.4 None I-X2/0.9 D1/0.28 120/110 comp 2A1/10 Compar. X1/0.4 None I-X310.9 D1/0.28 120/110 comp 3 A1/10

In Table 5, each of characters represents the following component:

<Resin>

A1: Resin A1, A2: Resin A2, X1: Resin X1

<Acid Generator>

B1-21: Salt represented by formula (B1-21), produced according to themethod as recited in JP2012-224611A1

B1-22: Salt represented by formula (B1-22), produced according to themethod as recited in JP2012-224611A1

IX-1: Salt represented by formula (IX-1), produced according to themethod as recited in JP2007-197718A1

IX-2: Salt represented by formula (IX-2), produced according to themethod as recited in JP2007-145822A1

IX-3: Salt represented by formula (IX-3), produced according to themethod as recited in JP2013-82893A1

<Salt of Formula (I)>

I-1: Salt represented by formula (I-1)

I-3: Salt represented by formula (I-3)

I-15: Salt represented by formula (I-15)

I-16: Salt represented by formula (I-16)

<Quencher>

D1: The compound of the following formula, which was manufactured byTokyo Chemical Industries, Co., Ltd.

<Solvent>

Mixture of the following solvents propyleneglycolmonomethylether acetate 265 parts propyleneglycolmonomethylether   20 parts 2-heptanone   20parts γ-butyrolactone  3.5 parts

<Evaluation>

Silicon wafers were each coated with “ARC-29”, which is an organicanti-reflective coating composition available from Nissan ChemicalIndustries, Ltd., and then baked at 205° C. for 60 seconds, to form a 78nm-thick organic anti-reflective coating. Each of the photoresistcompositions prepared as above was spin-coated over the anti-reflectivecoating so that the thickness of the resulting film became 100 nm afterdrying. The silicon wafers thus coated with the respective photoresistcompositions were each prebaked on a direct hotplate at the temperatureas listed in the column “PB” of Table 5 for 60 seconds. Using an ArFexcimer stepper (XT:1900G1 manufactured by ASML INC., NA=1.35, Annularσ_(out)=0.85 σ_(in)=0.65, X—Y polarization) and a mask for formingtrench pattern (pitch: 120 nm, trench width: 40 nm), each wafer havingthe respective resist film was subjected to exposure, with the exposurequantity being varied stepwise.

After the exposure, each wafer was subjected to post-exposure baking ona hotplate at the temperature as listed in the column “PEB” of Table 5for 60 seconds and then to development for 20 seconds at 23° C. withbutyl acetate (Tokyo Chemical Industries, Co., Ltd.) in the manner ofdynamic dispense method to produce a negative photoresist pattern.

In the following evaluation, effective sensitivity (ES) means theexposure quantity with which exposure using the above-mentioned maskprovides a pattern with 40 nm of the trench width after development.

<Evaluation of Focus Margin [DOF]>

Negative photoresist patterns were produced in the same manner asdescribed above except that exposure was conducted at the effectivesensitivity with the focus point distance being varied stepwise.

The focus range where the resulting photoresist patterns exhibited atrench pattern width of 40 nm±5% (between 38 nm and 42 nm) was taken asDOF (nm). The results were listed in Table 6.

TABLE 6 Ex. No. Composition No . DOF (nm) Ex. 5 1 90 Ex. 6 2 120 Ex. 7 3105 Ex. 8 4 135 Ex. 9 5 105 Ex. 10 6 150 Ex. 11 7 105 Ex. 12 8 150 Ex.13 9 105 Ex. 14 10 135 Comp. Ex. 1 Compar. Comp.1 60 Comp. Ex. 2 Compar.Comp.2 45 Comp. Ex. 3 Compar. Comp.3 60

The salt of the present invention is useful as a component for aphotoresist composition, and the photoresist composition containing thesalt of the present invention can provide photoresist patterns withexcellent DOF, which is suitable for fine processing of semiconductors.

What is claimed is:
 1. A salt represented by formula (I):

wherein Q¹ and Q² independently each represent a fluorine atom or aC1-C6 perfluoroalkyl group, R¹ and R² independently each represent ahydrogen atom, a fluorine atom or a C1-C6 perfluoroalkyl group, zrepresents an integer of 0 to 6, X¹ represents *—C(═O)—O—, *—O—C(═O)—,*—O—C(═O)—O— or —O—, where * represents a binding site to —C(R¹)(R²)— or—C(Q¹)(Q²)-, A¹ represents a C2-C36 divalent hydrocarbon group in whicha methylene group can be replaced by an oxygen atom, a sulfur atom, acarbonyl group or a sulfonyl group and in which a hydrogen atom can bereplaced by a substituent, R³ represents a hydrogen atom or a methylgroup, and Z⁺ represents an organic cation.
 2. The salt according toclaim 1 wherein X¹ represents *—C(═O)—O—.
 3. The salt according to claim1 wherein the divalent hydrocarbon group represented by A¹ has a C3-C18alicyclic hydrocarbon group.
 4. The salt according to claim 1 wherein R³is a hydrogen atom.
 5. An acid generator comprising the salt accordingto claim
 1. 6. A photoresist composition comprising the salt accordingto claim 1 as an acid generator and a resin which comprises a structuralunit having an acid-labile group.
 7. The photoresist compositionaccording to claim 6 which further comprises a salt generating an acidweaker in acidity than an acid generated from the acid generator.
 8. Aprocess for producing a photoresist pattern comprising the followingsteps (1) to (5): (1) a step of applying the photoresist compositionaccording to claim 6 on a substrate, (2) a step of forming a compositionfilm by conducting drying, (3) a step of exposing a composition film toradiation, (4) a step of baking the exposed composition film, and (5) astep of developing the baked composition film with an alkalinedeveloper, thereby forming a photoresist pattern.